Understanding space weather to shield society: A global road map for 2015-2025 commissioned by COSPAR and ILWS
Carolus J. Schrijver, Kirsti Kauristie, Alan D. Aylward, Clezio M. Denardini, Sarah E. Gibson, Alexi Glover, Nat Gopalswamy, Manuel Grande, Mike Hapgood, Daniel Heynderickx, Norbert Jakowski, Vladimir V. Kalegaev, Giovanni Lapenta, Jon A. Linker, Siqing Liu, Cristina H. Mandrini, Ian R. Mann, Tsutomu Nagatsuma, Dibyendu Nandi, Takahiro Obara, T. Paul O'Brien, Terrance Onsager, Hermann J. Opgenoorth, Michael Terkildsen, Cesar E. Valladares, Nicole Vilmer
aa r X i v : . [ phy s i c s . s p ace - ph ] M a r Understanding space weather to shield society:A global road map for 2015-2025 commissioned by COSPAR and ILWS
Carolus J. Schrijver a, ∗ , Kirsti Kauristie b, ∗ , Alan D. Aylward c , Clezio M. Denardini d , Sarah E. Gibson e , Alexi Glover f ,Nat Gopalswamy g , Manuel Grande h , Mike Hapgood i , Daniel Heynderickx j , Norbert Jakowski k , Vladimir V. Kalegaev l ,Giovanni Lapenta m , Jon A. Linker n , Siqing Liu o , Cristina H. Mandrini p , Ian R. Mann q , Tsutomu Nagatsuma r ,Dibyendu Nandi s , Takahiro Obara t , T. Paul O’Brien u , Terrance Onsager v , Hermann J. Opgenoorth w , MichaelTerkildsen x , Cesar E. Valladares y , Nicole Vilmer z a Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA94304, USA b Finnish Meteorological Institute, Finland c University College London, Dept. of physics and astronomy, Gower Street, London WC1E 6BT, UK d Instituto Nacional de Pesquisas Espaciais, Brazil e HAO/NCAR, P.O. Box 3000, Boulder, CO 80307-3000, USA f RHEA System and ESA SSA Programme Office, Darmstadt, Germany g NASA Goddard Space Flight Center, Greenbelt, MD, USA h Univ. of Aberystwyth, Penglais STY23 3B, UK i RAL Space and STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, UK j DH Consultancy BVBA, Diestsestraat 133/3, 3000 Leuven, Belgium k German Aerospace Center, Kalkhorstweg 53, 17235 Neustrelitz, Germany l Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia m KU Leuven, Celestijnenlaan 200B, Leuven 3001, Belgium n Predictive Science Inc., San Diego, CA, USA o National Space Science Center, Chinese Academy of Sciences, Haidian District, Beijing 100190, China p Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina q Dept. of physics, Univ. Alberta, Edmonton, AB, T6G 2J1, Canada r Space Weather and Environment Informatics Lab., National Inst. of Information and Communications Techn., Tokyo 184-8795, JAPAN s Center for Excellence in Space Sciences and Indian Institute of Science, Education and Research, Kolkata, Mohanpur 74125, India t Planetary plasma and atmospheric research center, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai 980-8578, Japan u Space science department/Chantilly, Aerospace Corporation, Chantilly, VA 20151, USA v NOAA Space Weather Prediction Center, USA w Swedish Institute of Space Physics, 75121 Uppsala, Sweden x Space Weather Services, Bureau of Meteorology, Australia y Institute for scientific research, Boston College, Newton, MA 02459, USA z LESIA, Observatoire de Paris, CNRS, UPMC, Universit´e Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France
Abstract
There is a growing appreciation that the environmental conditions that we call space weather impact the technologicalinfrastructure that powers the coupled economies around the world. With that comes the need to better shield societyagainst space weather by improving forecasts, environmental specifications, and infrastructure design. We recognizethat much progress has been made and continues to be made with a powerful suite of research observatories on theground and in space, forming the basis of a Sun-Earth system observatory. But the domain of space weather is vast -extending from deep within the Sun to far outside the planetary orbits - and the physics complex - including couplingsbetween various types of physical processes that link scales and domains from the microscopic to large parts of thesolar system. Consequently, advanced understanding of space weather requires a coordinated international approachto effectively provide awareness of the processes within the Sun-Earth system through observation-driven models. Thisroadmap prioritizes the scientific focus areas and research infrastructure that are needed to significantly advance ourunderstanding of space weather of all intensities and of its implications for society. Advancement of the existing systemobservatory through the addition of small to moderate state-of-the-art capabilities designed to fill observational gapswill enable significant advances. Such a strategy requires urgent action: key instrumentation needs to be sustained,and action needs to be taken before core capabilities are lost in the aging ensemble. We recommend advances throughpriority focus (1) on observation-based modeling throughout the Sun-Earth system, (2) on forecasts more than 12 hrsahead of the magnetic structure of incoming coronal mass ejections, (3) on understanding the geospace response tovariable solar-wind stresses that lead to intense geomagnetically-induced currents and ionospheric and radiation storms,and (4) on developing a comprehensive specification of space climate, including the characterization of extreme spacestorms to guide resilient and robust engineering of technological infrastructures. The roadmap clusters its implementationrecommendations by formulating three action pathways, and outlines needed instrumentation and research programs andinfrastructure for each of these. An executive summary provides an overview of all recommendations.
Keywords:
Space weather; COSPAR/ILWS Road Map Panel
Preprint for publication in Advances in Space Research March 23, 2015 ontents1 Introduction 52 Space weather: society and science 73 User needs 10 > ∗ Corresponding authors
Email address: [email protected] (Carolus J. Schrijver)
Appendix C.1 Achievements . . . . . . . . . 36Appendix C.2 Prospects for future work . . 37
Appendix D Research needs for the solar-heliospheric domain 39Appendix E Research needs for the geo-space domain 43
Appendix E.1 Magnetospheric field variabil-ity and geomagnetically-induced currents . 43Appendix E.2 Magnetospheric field variabil-ity and particle environment . . . . . . . . . 47Appendix E.3 Ionospheric variability . . . . 51
Appendix F Concepts for highest-priorityinstrumentation 54
Appendix F.1 Binocular vision for the coronato quantify incoming CMEs . . . . . . . . . 54Appendix F.2 3D mapping of solar field in-volved in eruptions . . . . . . . . . . . . . . 54Appendix F.3 Strong GICs driven by rapidreconfigurations of the magnetotail . . . . . 55Appendix F.4 Coordinated networks for ge-omagnetic and ionospheric variability . . . . 56Appendix F.5 Mapping the global solar field 57Appendix F.6 Determination of the founda-tion of the heliospheric field . . . . . . . . . 58Appendix F.7 Auroral imaging to map mag-netospheric activity and to study coupling . 58Appendix F.8 Observation-based radiationenvironment modeling . . . . . . . . . . . . 59Appendix F.9 Solar energetic particles inthe inner heliosphere . . . . . . . . . . . . . 60
Appendix G Acronyms 61Executive Summary
Space weather is driven by changes in the Sun’s mag-netic field and by the consequences of that variability inEarth’s magnetic field and upper atmosphere. This re-sults in a variety of manifestations, including geomagneticvariability, energetic particles, and changes in Earth’s up-permost atmosphere. All of these can affect society’s tech-nological infrastructures in different ways.2 pace weather is generally mild but some timesextreme.
Mild space weather storms can degrade electricpower quality, perturb precision navigation systems, in-terrupt satellite functions, and are hazardous to astronauthealth. Severe space storms have resulted in perturba-tions in the electric power system and have caused lossof satellites through damaged electronics or increased or-bital drag. For rare extreme solar events the effects couldbe catastrophic with severe consequences for millions ofpeople.
Societal interest in space weather grows rapidly:
As science and society increasingly recognize the impactsof space weather on the infrastructure of the global econ-omy, interest in, and dependence on, space weather in-formation and services grows rapidly. Apart from havingsocietal relevance, understanding space weather is an ex-citing science revealing how the universe around us works.
Space weather is an international challenge:
Sig-nificant scientific problems require substantial resources,with observations having to cover the terrestrial globe andspan the vast reaches of the heliosphere between Earth andthe Sun.
Mitigating against the impacts of space weathercan be improved by designing less susceptible, more re-silient technologies, combined with better environmentalknowledge and more reliable forecasts. This roadmap out-lines how we can achieve deeper understanding and bet-ter forecasts, recognizing that the expectations for spaceweather information differ between societal sectors, andthat capabilities to observe or model space weather phe-nomena depend on available and anticipated technologies.
The existing observatories that cover much ofthe Sun-Earth system provide a unique startingpoint:
Moderate investments now that fill key capabil-ity gaps can enable scientific advances that could not beotherwise achieved, while at the same time providing apowerful base to meet many operational needs. Improvingunderstanding and forecasts of space weather requires ad-dressing scientific challenges within the network of physicalprocesses that connect the Sun to society. The roadmapteam identified the highest-priority areas within the Sun-Earth space-weather system whose advanced scientific un-derstanding is urgently needed to address current spaceweather service user requirements. The roadmap recom-mends actions towards such advanced understanding, fo-cusing on the general infrastructure to support research aswell as on specific concepts for instrumentation to meetscientific needs.
Roadmap recommendations:
Research: observational, computational, & theoretical needs:
1. Advance the international Sun-Earth system obser-vatory along with models to improve forecasts basedon understanding of real-world events through thedevelopment of innovative approaches to data incor-poration, including data-driving, data assimilation,and ensemble modeling; 2. Understand space weather origins at the Sun andtheir propagation in the heliosphere, initially priori-tizing post-event solar eruption modeling to developmulti-day forecasts of geomagnetic disturbance timesand strengths, after propagation through the helio-sphere;3. Understand the factors that control the generationof geomagnetically-induced currents (GICs) and ofharsh radiation in geospace, involving the couplingof the solar wind disturbances to internal magneto-spheric processes and the ionosphere below;4. Develop a comprehensive space environment specifi-cation, first to aid scientific research and engineeringdesigns, later to support forecasts.
Teaming: coordinated collaborative research environment:
I Quantify vulnerability of humans and of society’s in-frastructure for space weather by partnering withuser groups;II Build test beds in which coordinated observing sup-ports model development;III Standardize (meta-)data and product metrics, andharmonize access to data and model archives;IV Optimize observational coverage of the Sun-societysystem.
Collaboration between agencies and communities:
A Implement an open space-weather data and informa-tion policy;B Provide access to quality education and informationmaterials;C Execute an international, inter-agency assessment ofthe state of the field on a 5-yr basis to adjust prior-ities and to guide international coordination;D Develop settings to transition research models to op-erations;E Partner with the weather and solid-Earth communi-ties to share lessons learned.The roadmap’s research recommendations are expandedin three pathways that reflect a blend of the magnitudeof societal impact, scientific need, technological feasibil-ity, and likelihood of near-term success. Each pathwayneeds recommendations of any preceding it implementedto achieve full success, but can be initiated in parallel.The pathways are designed to meet the variety of differen-tial needs of the user communities working with differenttypes of impacts. Recommendations within each pathwayare grouped into actions that can be taken now, soon, oron a few-year timescale, each listed in priority order withinsuch group.Pathway I recommendations: to obtain forecasts morethan 12 hours ahead of the magnetic structure of incom-ing coronal mass ejections and their impact in geospaceto improve alerts for geomagnetic disturbances and strongGICs, related ionospheric variability, and geospace ener-getic particles:
Maintain existing essential capabilities: solar magnetic maps (GBO, SDO) and EUV/X-rayimages at arcsec and few-second res. (SDO; Hinode),and solar spectral irradiance observations; • solar coronagraphy, best from multiple perspectives(Earth’s view and L1: GBO and SoHO; and well offSun-Earth line: STEREO); • in-situ measurements of solar-wind plasma and mag-netic field at, or upstream of, Sun-Earth L1 (ACE,SoHO; DSCOVR); • for several years, continue to measure the interactionacross the bowshock-magnetopause (as now with Clus-ter/ARTEMIS/THEMIS; soon with MMS), to bet-ter understand wind-magnetosphere coupling; • satellite measurements of magnetospheric magneticand electric fields, plasma parameters, soft auroraland trapped energetic particle fluxes (e.g., Van-AllenProbes, LANL satellites, GOES, ELECTRO-L, POES,DMSP); • ground-based sensors for solar, heliospheric, mag-netospheric, and iono-/thermo-/mesospheric data tocomplement satellite data. Model capability, archival research, or data infrastructure: • near-real time, observation-driven 3D solar active-region models of the magnetic field to assess desta-bilization and to estimate energies; • data-driven models for the global solar surface-coronalfield; • data-driven ensemble models for the magnetized so-lar wind; • data assimilation techniques for the global ionosphere-magnetosphere-atmosphere system using ground andspace data for nowcasts and near-term forecasts ofgeomagnetic and ionospheric variability, making op-timal use of selected locations where laboratory-liketest beds exist or can be efficiently developed; • coordinated system-level research into large-scale rapidmorphological changes in Earth’s magnetotail andembedded energetic particle populations and theirlinkage to the ionosphere; • system-level study of the mechanisms of the par-ticle transport/acceleration/losses driving currentsand pressure profiles in the inner magnetosphere; • stimulate research to improve global geospace mod-eling beyond the MHD approximation (e.g., kineticand hybrid approaches); • develop the ability to use solar chromospheric andcoronal polarimetry to guide full-Sun corona-to-heliospherefield models. Deployment of new/additional instrumentation: • binocular imaging of the solar corona at ∼ ◦ to 20 ◦ separation between perspectives; • observe the solar vector-field at and near the surfaceand the overlying corona at better than 200-km reso-lution to quantify ejection of compact and low-lyingcurrent systems from solar active regions; • (define criteria for) expanded in-situ coverage of theauroral particle acceleration region and the dipole-tail field transition region (building on MMS) to de-termine the magnetospheric state in current (THEMIS,Cluster) and future high-apogee constellations, usinghosted payloads and cubesats where appropriate; • (define needs, then) increase ground- and space-basedinstrumentation to complement satellite data of themagnetospheric and ionospheric variability to covergaps (e.g., in latitude coverage and over oceans); • an observatory to expand solar-surface magnetogra-phy to all latitudes and off the Sun-Earth line [start-ing with Solar Orbiter]; • large ground-based solar telescopes (incl. DKIST)to perform multi-wavelength spectro-polarimetry toprobe magnetized structures at a range of heights inthe solar atmosphere, and from sub-active-region toglobal-corona spatial scales; • optical monitors to measure global particle precipi-tation to be used in assimilation models for geomag-netic disturbances and ionospheric variability.Pathway II recommendations: to understand the parti-cle environments of (aero)space assets leading to improvedenvironmental specification and near-real-time conditions.With the Pathway-I requirements implemented: Maintain existing essential capabilities: • LEO to GEO observations of electron and ion pop-ulations (hard/ ∼ MeV and soft/ ∼ keV; e.g., GOES,. . . ), and of the magnetospheric field, to support im-proved particle-environment nowcasts; • maintain a complement of spacecraft with high res-olution particle and field measurements (such as theVan Allen Probes). Model capability, archival research, or data infrastructure: • specify the frequency distributions for fluences of en-ergetic particle populations [SEP, RB, GCR] for avariety of orbital conditions, and maintain archivesof past conditions; • develop, and experiment with, assimilative integratedmodels for radiation-belt particles towards forecast4evelopment including data from ionosphere, ther-mosphere and magnetosphere and below, and vali-date these based on archival data. Deployment of new/additional instrumentation: • deploy high- and low-energy particle and electro-magnetic field instruments to ensure dense spatialcoverage from LEO to GEO and long-term coverageof environment variability (incl., e.g., JAXA’s ERG).Pathway III recommendations: to enable pre-event fore-casts of solar flares and coronal mass ejections, and re-lated solar energetic particle, X-ray, EUV and radio waveeruptions for near-Earth satellites, astronauts, ionosphericstorm forecasts , and polar-route aviation, including all-clear conditions. Maintain existing essential capabilities (in addition to Path-way-I list): • solar X-ray observations (GOES); • observe the inner heliosphere at radio wavelengths tostudy shocks and electron beams in the corona andinner heliosphere; • maintain for some years multi-point in-situ observa-tions of SEPs on- and off Sun-Earth line throughoutthe inner heliosphere (e.g., L1, STEREO; includingground-based neutron monitors); • maintain measurements of heavy ion composition (L1:ACE; STEREO; near-future: GOES-R). Model capability, archival research, or data infrastructure: • develop data-driven predictive modeling capabilityfor field eruptions from the Sun through the innerheliosphere; • investigate energetic particle energization and prop-agation in the inner heliosphere, aiming to develop atleast probabilistic forecasting of SEP properties [cf.Pathway-I for heliospheric data-driven modeling]; • ensemble modeling of unstable active regions to un-derstand energy conversions into bulk kinetic mo-tion, photons, and particles. Deployment of new/additional instrumentation: • new multi-point in-situ observations of SEPs off Sun-Earth line throughout the inner heliosphere to un-derstand population evolutions en route to Earth(e.g., Solar Orbiter, Solar Probe Plus). Concepts for new priority instrumentation:
Pathway I:
1. Quantify the magnetic structure involved in nascentcoronal ejections though binocular vision of the source-region EUV corona, combined with 3D mapping ofthe solar field involved in eruptions through (near-)surface vector-field measurements and high-resolutionatmospheric imaging; 2. Understand the development of strong geomagnetically-induced currents through magnetotail-to-ionospherein-situ probes, complemented with coordinated ground-based networks for geomagnetic and ionospheric vari-ability;3. Map the global solar field, and use models and ob-servations to determine the foundation of the he-liospheric field, to drive models for the solar-windplasma and magnetic field;4. Image the aurorae as tracers supporting the quantifi-cation of the state of the magnetosphere-ionospheresystem;
Pathway II:
Pathway III:
1. Introduction
As technological capabilities grow, society constructs arapidly deepening insight into the forces that shape theenvironment of our home planet. With that advancingunderstanding comes a growing appreciation of our vul-nerability to the various attributes of space weather. Thevariable conditions in what we think of as ”space” drivesociety to deal with the hazards associated with living inclose proximity to a star that sustains life on Earth evenas it threatens humanity’s technologies: the dynamic mag-netism manifested by the Sun powers a sustained yet vari-able solar wind punctuated by explosive eruptions that attimes envelop the planets, including Earth, in space stormswith multiple potentially hazardous types of conditions.Powerful magnetic storms driven by solar eruptions en-danger our all-pervasive electric power grid and disruptthe many operational radio signals passing through ourplanet’s upper atmosphere (including the satellite naviga-tion signals that is now vital to society). Energetic particlepopulations can lead to malfunctions of satellites and putastronauts at risk.These solar-powered effects in Earth’s environment, col-lectively known as space weather (with the shorthand no-tation of SWx), pose serious threats to the safe and ef-ficient functioning of society. In recognition of the mag-nitude of the hazards, governments around the world areinvesting in capabilities to increase our awareness of spaceweather, to advance our understanding of the processesinvolved, and to increase our ability to reliably forecast,prepare for, design to, and respond to space weather. Sci-entists with a wide variety of expertise are exploring themagnetism of the Sun from its deep interior to the outer-most reaches of the planetary system, and its impacts onplanetary environments. Great strides forward have been5ade towards a comprehensive study of all that happensbetween the magnetized interior of the Sun and mankind’stechnological infrastructure. An ensemble of in-situ andremote-sensing instruments on the Earth and in space isuncovering and quantifying many aspects of evolving spaceweather from Sun to Earth. These instruments monitorthe progress of space weather across the vast interplan-etary volume known as the heliosphere and observe howspace weather impacts pass through Earth’s magnetic co-coon and into Earth’s upper atmosphere. But this en-semble is subject to major observational gaps and needsto be strengthened by improved coordination and integra-tion. Scientific research and observations are increasinglycombined in computer models and analyses that describeand forecast space weather conditions, aiming to protectsociety from the dangers of space storms, but still lackingessential capabilities in many parts of the overall Sun-to-Earth chain.Similar to terrestrial weather, space weather occurs allthe time and it frequently affects our technological infras-tructure in ways that are not catastrophic, but that arecostly in their aggregate value to the global economy. Im-pacts on satellite-based navigation and timing capabilitiesor satellite communications affect users of the global nav-igation satellite system (GNSS) from precision agricultureto national security. Space weather is a serious constrainton the resilience of GNSS and thus a vital issue for ahuge and growing range of economic activities: impactsare seen throughout the multitude of industry sectors thatuse satellite-based navigation systems, including on theaviation industry as it seeks to exploit GNSS as a way tooptimize aircraft routing and hence airspace capacity; onthe development of self-driving cars that rely on GNSS; onthe accuracy of maritime drilling operations; on the timingsystems that synchronize power and cell-phone networks insome countries, and on the finance industry as it moves tomicrosecond-resolution time stamping of financial trans-actions. Satellite anomalies and failures due to radiationstorms impact the flow of information from satellite phonesto weather monitoring, and from scientific exploration tointelligence monitoring. Space-weather impacts on the all-pervasive electric power grids have an even larger reach,with impacts ranging from rather frequent power-qualityvariations (such as voltage variations, frequency drifts andharmonics, and very short interruptions) to potential in-frequent but major power interruptions.Also similar to terrestrial weather, extreme space stormsare expected to have major impacts. With our sensi-tive electrical, electronic, and space-based technologies ex-panding rapidly into a tightly woven network of applica-tions we are not certain about the magnitudes of the im-pacts of extreme space weather, but studies suggest thatwe should be seriously concerned. For example, a singleunusually severe geomagnetic storm has been hypothesizedto cause long-term power outages to tens of millions of citi-zens of multiple countries and is thus listed among nationalsecurity risks (e.g., the UK national risk register). Perma- nent loss of multiple satellites by severe energetic-particlestorms has significant consequences for communications,surveillance, navigation, and national security.Although small compared to the risks deemed to be in-volved, the resources required to understand space weatherand its impacts are substantial: the domain to be coveredfor successful space-weather forecasting and preparednessis vast, the physics of the intricately coupled processes in-volved is complex, and the diversity of the rapidly-growinguser communities crosses all aspects of society and itsglobally-connected economy. Moreover, the impacts ofspace weather span the globe. For those reasons, an inter-national approach is paramount to successfully advancingour scientific understanding of space weather. This real-ization prompted the Committee on Space Research (CO-SPAR) of the International Council for Science (ICSU)and the International Living With a Star (ILWS) SteeringCommittee to commission a strategic assessment of how toadvance the science of space weather with the explicit aimof better meeting the user needs around the globe. Thisreport is the outcome of that activity.In the spring of 2013, the leadership of COSPAR andILWS appointed a team of experts charged to create thisroadmap (see Appendix A for the process followed). Themission statement by COSPAR’s Panel on Space Weather(PSW) and the ILWS steering committee asks the team to“[R]eview current space weather capabilities and identifyresearch and development priorities in the near, mid andlong term which will provide demonstrable improvementsto current information provision to space weather serviceusers”, thereby expressing a focus on the terrestrial envi-ronment. The charge continued with the expectation that“the roadmap would cover as minimum: • Currently available data, and upcoming gaps • Agency plans for space-based space weather data(national and international): treating both scientificand monitoring aspects of these missions. • Space and ground based data access: where currentdata is either proprietary or where the geographiclocation of the measurement makes data access dif-ficult • Current capability gaps which would provide a markedimprovement in space weather service capability.The outcome should centre on a recommended approach tofuture developments, including coordination and address-ing at least:1. Key science challenges2. Data needs, space and ground based3. Smooth and organised transition of scientific devel-opments into reliable services”.For the purpose of this roadmap we use the followingdefinition:
Space weather refers to the variable state of the oupled space environment related to changing conditionson the Sun and in the terrestrial atmosphere, specificallythose conditions that can influence the performance and re-liability of space-borne and ground-based technological sys-tems, and that can directly or indirectly endanger humanwell-being. Aspects of space situational awareness such asspace debris in Earth orbit and asteroids or other near-Earth objects are not considered in this roadmap. Thestructure under which the roadmap team operates impliesthat it focus exclusively on civilian needs, although manyof its conclusions are likely directly pertinent to the secu-rity and military sectors of society.This roadmap identifies high-priority challenges in keyareas of research that are expected to lead to a better un-derstanding of the space environment and an improvementin the provision of timely, reliable information pertinent toeffects on space-based and ground-based systems. Amongthose is the realization that we cannot at present use obser-vations of the Sun to successfully model the magnetic fieldin coronal mass ejections (CMEs) en route to Earth, andthus we cannot forecast the strength of the perturbation ofthe magnetospheric field that will occur. Another exampleis that we understand too little of magnetic instabilities toforecast the timing and energy release in large solar flaresor in intense (sub)storms in geospace. Advances in theseareas will strengthen our ability to understand the entireweb of physical phenomena that connect Sun and Earth,working towards a knowledge level to enable forecasts ofthese phenomena at high skill scores.The roadmap prioritizes those advances that can bemade on short, intermediate, and decadal time scales, iden-tifying gaps and opportunities from a predominantly, butnot exclusively, geocentric perspective. This roadmap doesnot formulate requirements for operational forecast or real-time environmental specification systems, nor does it ad-dress in detail the effort required to utilize scientific ad-vances in the improvement of operational services. Thisroadmap does, however, recognize that forecasts (whetherin near-real time or retrospectively) can help uncover gapsin scientific understanding or in modeling capabilities, andthat test beds for forecast tools serve both to enable quan-titative comparison of competing models and as stagingenvironment for the phased transition of research tools toan operational application.The main body of this roadmap is complemented byAppendices that contain more detailed or supplemental in-formation, describe the roadmap process, summarize sci-entific advances and needs, and outline instrumentationconcepts. Appendix G provides a list of the acronyms andabbreviations used in this document.
2. Space weather: society and science
The task defined by COSPAR and ILWS is founded onthe realization that space weather is a real and permanenthazard to society that needs to be, and can be, addressed by combining scientific research with engineering ingenu-ity: protecting society from space weather requires thatwe adequately understand the physical processes of spaceweather, that we characterize the conditions to which tech-nological infrastructures need to be designed, that we learnto effectively forecast space weather, and that the conse-quences of acting on such forecasts are accepted as neces-sary for the protection of societal infrastructure.Societal use of, and dependence on, ground-based elec-trical systems and space-based assets has grown tremen-dously over the past decades, by far outpacing populationgrowth as society continues to grow its electrical/electronicand space-based technologies. Global electricity use has in-creased by a factor of about 1.6 over the 15-year period be-tween 1997 and 2012 (International Energy Agency, 2013).The global satellite industry revenue has multiplied by afactor of about 4.2 over that period (to US$190 billion peryear for 2012, part of a total value of US$304 billion forthe overall space industry, with over 1,000 operating satel-lites from over 50 countries; Satellite Industry Association,2013). In contrast, the global population grew by approxi-mately 20% over that period (Population reference bureau,2013), demonstrating our increasing use of electrical powerand satellite-based information per capita.With that growth in electrical/electronic and space-based technologies comes increasing vulnerability to spaceweather: where a century ago the main risk was associatedwith the telegraph systems we now see impacts in the elec-tric power grid, in satellite functionality, in the accuracy ofnavigation and timing information, and in long-range high-frequency (HF) radio communication. We see an increas-ing interest in understanding space weather impacts andthe threats these pose are spread over a variety of civiliansectors (and non-civilian sectors that lie beyond the scopeof this Roadmap). Selected reports on these impacts (thatthemselves provide information on more literature on thesubject) are compiled in an on-line resource list that ac-companies this report; that resource list also includes aglossary of solar-terrestrial terms , and links to a NationalGeographic introduction to space weather accessible viaYouTube , and lectures related to space weather, its im-pacts, and its science in the NASA Heliophysics SummerSchool .The reality of the threat to society posed by spaceweather is increasingly acknowledged - reflected, for ex-ample, in the exponential growth of the number of webpages on space weather (totaling over 130,000 new entriesin 2013; see Figure 1) and in the number of customers sub-scribing to alert and forecast services (exceeding, for exam-ple, 44,000 for the US Space Weather Prediction Center).A core difficulty facing any study that attempts a cost-benefit analysis for space weather is inadequate knowledge ∼ schryver/COSPARrm/SWlibrary.html ∼ schryver/COSPARrm/SWlibrary.html igure 1: Number of publications per year with “space weather”in the abstract in NASA/ADS (blue; left axis), and the number ofweb sites returned by a Google search for “space weather” withincalendar years (since 2003) in thousands (red; right axis). of the technological and economic impacts of ongoing spaceweather and of the risk posed by extreme space storms.This hampers the quantitative identification of the mostsignificant impacts of space weather and consequently theprioritization of the research areas and the deploymentof infrastructure to protect against space weather. Forour roadmap, existing assessments of threats and impactscompiled by organizations currently engaged in providingspace weather infromation to affectd sectors proved ade-quate for a prioritization of recommendations, but achiev-ing a quantification of the SWx impact on societal tech-nologies is important for the process of allocating the re-quired resources for research and forecasting, and of deter-mining what sectors of society should be involved in appro-priating which resources. For example, although the threatposed by geomagnetic storms is broadly recognized as real(e.g., Krausmann, 2011; Langhoff and Straume, 2012), es-tablishing the vulnerability and consequences of such anevent has proven to be very difficult (Space Studies Board,2008; DHS Office of Risk Management and Analysis, 2011;JASON, 2011), hampering a cost-benefit assessment of in-vestments that could make impacted systems less vulner-able by suitable engineering or by improved forecasting(DHS Office of Risk Management and Analysis, 2011).Like terrestrial weather, space weather manifests itselfas a variety of distinct phenomena, and like terrestrialweather, it ranges from benign to extremely severe. Mostfrequently, space weather is very weak in intensity withapparently little impact on technology. Strong, severe, orextreme geomagnetic conditions (as measured by the Kpindex, on NOAA’s G scale occur only 5% of days througha solar magnetic cycle. Even though there are no reportsof catastrophic failures in the US high-voltage power grid,one study finds that there appears to be an increase by40% ±
20% in insurance claims for industrial electrical andelectronic equipment on the 5% most geomagnetically ac- tive days (as measured by the rate of change in the geo-magnetic field strength) relative to quiet days, and thereis an increase of 30% ±
10% in the occurrence frequencyof substantial disturbances in the US high-voltage powergrid (Schrijver et al., 2014). Another study suggests that,overall, approximately 4% of the disturbances in the UShigh-voltage power grid reported to the US Departmentof Energy appear to be attributable to strong but notextreme geomagnetic activity and its associated geomag-netically induced currents (GICs; Schrijver and Mitchell,2013). More such studies are needed to validate thesefindings and particularly to help uncover the pathways bywhich these impacts occur (a point to which we return inour recommendations below).Other aspects of space weather can adversely affectsatellites. Severe solar energetic-particle (SEP) storms,for example, impact satellites directly, while expansion ofthe terrestrial upper atmosphere by magnetospheric vari-ability (through Joule heating) may affect low-orbitingsatellites by modifying their orbits through increased dragwhich is an issue for on-orbit operations, collision avoid-ance, and could eventually lead to early re-entry (e.g.,Rodgers et al., 1998). A series of such storms during the2003 October-November time frame, for example, saw con-siderable impacts on satellites through electronic single-event upsets (SEUs), solar-array degradation, modified or-bit dynamics for spacecraft in low-Earth orbits, and noiseon both housekeeping data and instrument data. Anothermanifestation of space weather is the enhancement of ra-diation belt (RB) particles and of magnetospheric plasmathat cause charging/discharging phenomena or state up-sets in satellite electronics. For 34 Earth and space sciencemissions from NASA’s Science Mission Directorate, for ex-ample, 59% of the spacecraft experienced such effects (Bar-bieri and Mahmot, 2004). A graphic laboratory demon-stration of discharging inside dielectric materials (a criti-cal space weather impact for satellites in geosynchronousand middle Earth orbit) is available on YouTube .A third impact for space weather occurs via severemodification of trans-ionospheric signals by highly variableplasma density in space and time, thus affecting customersof GNSS services. The economic impact of this type ofspace weather has yet to be investigated, being compli-cated by the fact that it will mostly occur well downstreamof the immediate service providers and also by the factthat GNSS technology is rapidly evolving even as the to-tal numbers of users and uses increases, increasingly in lay-ered applications that may hide just how GNSS-dependenta system is.The threat posed to society by the most severe spacestorms that occur a few times per century is largely un-known and the magnitude of such a threat is consequentlyhighly uncertain: the technological landscape evolves sorapidly that our modern-day highly-interconnected soci-etal infrastructure has not been subjected to the worst http://youtu.be/-EKdxzZ52zU thatwas initiated in 2005 and that exceeded 40,000 individ-ual subscribers early in 2014. A survey of the subscribersto the SWPC service in 2013 enabled an assessment ofthe interests from the user side (Schrijver and Rabanal,2013), which concluded that “[s]pace weather informationis most commonly obtained for reasons of [indirect im-pacts through interruptions of power or communicationson] human safety and continuity or reliability of opera-tions. The information is primarily used for situationalawareness, as aid to understand anomalies, to avoid im-pacts on current and near-future operations by implement-ing mitigating strategies, and to prepare for potential near-future impacts that might occur in conjunction with con-tingencies that include electric power outages or GPS per-turbations. Interest in, anticipated impacts from, and re-sponses to the three main categories of space weather [-geomagnetic, radiation, and ionospheric storms -] are quiteuniform across societal sectors. Approximately 40% of therespondents expect serious to very serious impacts fromspace weather events if no action were taken to mitigateor in the absence of adequate space weather information.The impacts of space weather are deemed to be substan- http://pss.swpc.noaa.gov
3. User needs
The complexity of the interconnected system of phys-ical processes involved in space weather precludes a sin-gle, comprehensive, yet understandable and concise ex-ploration of the network as a whole. To effectively andefficiently address its charge, the roadmap team thereforedeveloped a strategy that focuses on three largely distinctspace weather phenomena with largely complementary im-pact chains into societal technologies: a) geomagnetic dis-turbances that drive electric currents through the electricpower infrastructure, b) variability in the ionospheric elec-tron density that impacts positioning and navigation sys-tems, and c) energetic particles for space assets, astro-nauts and stratospheric air traffic (with possible impactson passengers, crews, and avionics). Many other systemsare susceptible to these and other manifestations of spaceweather, whether directly or indirectly, but together thesethree chains encompass the most significant impacts andtogether they cover most of the research and forecast needsthat would be needed for the other types of impacts. Fig-ure 2 lays out these three chains side by side, with anapproximate vertical time axis to map the user needs and the physical domains involved. Some details of the impacttracing exercise are described in Appendix B.The societal needs for space weather information, in-cluding forecasts, are rapidly growing as witnessed by theexponential growth in the US NOAA/SWPC product cus-tomer base, the growth in space-weather research publica-tions (Fig. 1), and in the variety of strategic studies andreports (see Section 2). Of the subscribers to the SWPCelectronic alert and forecast services customers, only about20% deem the quality and content of the available informa-tion adequate (Schrijver and Rabanal, 2013). Even thoughabout two-thirds of these customers considers the informa-tion “generally adequate”, the forecasts leave much to bedesired owing to a lack of scientific understanding in mul-tiple sectors of the Sun-Earth connected system and to apoor knowledge of the magnitude of impacts.When provided with warnings of significant space weatherstorms, the subscribers to space weather information ser-vices typically either increase monitoring or implementpreventive action in roughly comparable fractions. In-creased availability of real-time information and increasedspecificity and accuracy of the forecasts should enable moretargeted and effective actions, while lowering the costs as-sociated with false alarms. Improved quality of forecastsand improved quantification of the system vulnerabilitycan put society on the desirable path of either efficientlyacting on space-weather forecasts as one would on terres-trial weather forecasts, or by improving system design andoperations that reduce vulnerability as done for other nat-ural forces, at least up to some value that is ideally basedon a well-founded cost-benefit risk assessment.In the three technological infrastructures of our impacttracing exercise different approaches to mitigate the SWxrisk are used and consequently also the needs of SWx ser-vices supporting the societal sectors using these infrastruc-tures are different:
The electric power sector is primarily affected by geo-magnetically-induced currents (GICs), which can push trans-formers off their linear domains leading to dissipative heatthat can damage transformers, and to generation of har-monics of the primary 60-Hz or 50-Hz wave. These har-monics can cause protective systems to trip and can af-fect systems operated by power customers downstream inthe distribution network. Power-grid operators can reduceor prevent damage by optimizing design, by introducingprotective equipment, or by redistributing and changingthe power-generation resources so that fewer long-distancetransfers are needed and more near-locally-generated poweris available to counter frequency and voltage modulations.Other solutions, such as that adopted in the UK with itsrelatively compact power system, are to bring all availablegrid links into operation in order to maximize redundancyand to spread GICs over the whole system, reducing theimpact on individual system elements. To optimize systemprotection, improved knowledge of the impacts is needed,10 igure 2: Overview of the primary impacts and their societal sectors of space weather. The red shading in the background indicates thepriority needs for the user communities behind each of the impacts, differentiated by time scale for forecast or for archival information asshown on the left. Text boxes identify the primary needed observations, archival measurements, and models to complete the impact chain,differentiated (using color, see legend) by solar, heliospheric, and geospace domains. including extreme-event scenarios, which requires histori-cal and pre-historical information.In order to effectively plan the power grid operationssubject to strong GMDs, the sector has expressed a needfor a reliable warning at least half a day ahead of com-ing storms, preferably with a reliable forecast of the mag-nitude and duration of the geomagnetically induced cur-rents (GICs). The propagation time for CMEs from Sunto Earth is typically of order 2-4 days, and even for thefastest known events exceeds 0.75 days. Hence, the needfor a forecast for CME arrivals about 12 hours ahead re-quires the formulation of a forecast well after a solar erup-tion has occurred (and should have been observed), butlong before it approaches geospace (here defined loosely asa domain encompassing everything from Earth’s middleatmosphere out to the upstream magnetopause and down-stream beyond the magnetotail), or any sensors currentlyavailable upstream of Earth. In Figure 2, the highest-priority user needs for thepower sector are indicated by red-shaded areas in the barin the background of the left-hand column. The deepestred areas for GIC service needs are in the forecasts withhalf-day lead times and in the specifications of extremeconditions based on archival information on past condi-tions. Interests in 12hrs-ahead warnings of GMDs arealso expressed by industries using the geomagnetic fielddirectly, including mining, drilling, and surveying. Wenote that addressing the needs of the GMD/GIC and iono-spheric communities also provides information on modula-tions of satellite drag caused by current dissipation withinthe ITM domain of Earth’s upper atmosphere.
Positioning and navigation services such as providedby the GNSS are most affected by ionospheric electron-density variability via strong coupling with magnetospheric11nd thermospheric changes driven by CMEs and high-speed solar wind streams or related to X-ray and extremeultraviolet (EUV) eruptions on the solar surface or (of par-ticular importance for the low-latitude ionosphere) upwardpropagating waves originating in the lower Earth atmo-sphere. Ionospheric range errors of up to 100m in singlefrequency GNSS applications can be largely mitigated byproper ionospheric models, or more accurately by regionaland/or global maps of the total electron content (TEC) orby 3D electron density reconstructions provided in near-real time (i.e., within minutes, or even seconds, of measure-ments being made). Precise and safety-critical positioningand navigation, as required, for instance, in aviation, suf-fer in particular from steep spatial gradients and temporalvariability of the plasma density. Thus, plasma bubblesand small-scale electron density irregularities (known asplasma turbulence) may cause strong fluctuations in signalamplitude and phase that are called radio scintillations; se-vere phase scintillation may even cause loss of phase lockof the signal.In professional GNSS services position accuracy is sup-ported by augmentation systems. These include (a) widearea satellite-based augmentation systems (SBAS) such asEGNOS in Europe, WAAS in North America, and MSASin Asia), and (b) ground-based augmentation systems thatprovide local services such as around sea- and air-ports.These systems monitor the accuracy and reliability of thepositioning signal and provide an integrity flag that canwarn GNSS users when back-up solutions for navigationmust be used (well demonstrated by the WAAS systemduring the Halloween storms of 2003). SBAS systemsbring a further vulnerability to space weather in that theirmessages must cross the ionosphere as both uplink to, anddownlink from, a satellite hosting an SBAS relay system.Both uplink and downlink are vulnerable to ionosphericradio scintillation. Similarly the increasing use of satel-lite links for communication with, and tracking of, aircraftopens up a vulnerability to scintillation. On the otherhand, forecasts of plasma perturbations have a great po-tential for mitigating space weather impact on radio sys-tems by alerting operators and customers of telecommuni-cation and navigation systems and remote sensing radarsas well. Thus, for example, airplanes whose HF and satel-lite communication may be disturbed heavily typically re-quire - as is the case for weather conditions - a forecastof ionospheric electron density variability a good fractionof a day ahead of time. Correcting for, or accommodat-ing, these impacts on HF telecommunication and GNSSsignals requires an extensive network of ionospheric mea-surement devices, rapid modeling, and rapid dissemina-tion of correction information. The needs of most of theGNSS customers thus lands in the time domain from cur-rent state (nowcast) to of order an hour ahead (see middlecolumn of Figure 2), but somewhat longer-term forecastsare valuable, for example, for planning purposes of opera-tions and emergency response activities. These needs willevolve as dual-frequency and/or differential GNSS usage become more widespread.Another aspect of ionospheric electron density variabil-ity driven by space weather is radio wave absorption inthe frequency range below about 30 MHz. This ariseswhen high-energy inputs to the atmosphere generate ad-ditional ionization at altitudes around 90 km altitude andbelow known as D region in the ionosphere. In this re-gion the neutral density is high and therefore also the col-lision frequency between charged particles and neutrals.Thus, charged particles that are excited by electromag-netic waves in the frequency range mentioned above losetheir energy very fast, i.e. the radio wave will be absorbedor at least heavily damped. D region ionization can arisefrom a variety of high-energy space weather phenomena:intense bursts of X-rays from solar flares and the precip-itation of solar energetic particles (SEP). These have thepossibility to disrupt HF communications that are used bycivil aviation in remote regions, especially over the oceansand poles. The impact of flare X-rays appears to be a nui-sance rather than a serious problem, since they produceonly short-lived disruptions (of order an hour) that canbe mitigated by well-established procedures and by useof satcom applications as an increasingly common backup.However, the impact of SEPs is very significant as their im-pact is greatest in the polar regions (where satcom backupis not currently available) and is long-lived (up to days)so that procedural measures are insufficient. Thus polarflights are diverted to other less vulnerable routes duringSEP events, imposing significant extra costs on airlines(around $100k per diversion; National Research Council,2008). This problem could be mitigated in the future withincreased use of satcom the polar regions, including use ofthe potential Canadian PCW (Polar Communications andWeather) satellite system.The presence of a strong D region also impacts low-frequency navigation systems by advancing the arrival ofskywave, i.e., the LF signal reflected from the ionospherethat interferes with ground-wave, which is the LF sig-nal propagating as an interface wave along the surface ofthe Earth. Thus older LF systems such as LORAN andDECCA were prone to major position errors, for exam-ple during REP events at mid-latitudes. However, mostof these old systems have now been taken out of servicein favor of more accurate GNSS. New LF systems, suchas the eLORAN system now deployed operationally in theUK, can match the accuracy of GNSS, but like GNSS in-clude integrity checks to warn when location data are notaccurate.
The impacts of high-energy solar-energetic and radiation-belt particles are strongest in space-based assets, includingsatellites and astronauts, but extend to stratospheric air-craft as these rely increasingly on ever-smaller electronicssystems distributed throughout the vehicle. Such effectsare caused by energetic particles (those of galactic ori-gin all the time, and SEP where these have strong fluxes12t energies >
500 MeV) that penetrate to the Earth’s at-mosphere and interact with atmospheric neutral particles.Such collisions produce cascades of neutrons and ions thatcan interact with aircraft to produce single event effects(SEE) and increased dose rate for passengers and crew.During SEP events radiation effects at aircraft trajecto-ries are strongest at high latitudes where solar particlescan more easily penetrate. Whether there are detrimentaleffects on the health of airline crews and passengers re-mains to be established, but assessing the risk, regardlessof the outcome of the studies, is clearly of importance.The requirements from the involved sectors separatesomewhat by type of radiation, as indicated in Figure 2.In the background, with mostly longer-term and moderatevariability, is the galactic cosmic ray (GCR) population,for which archival data spanning centuries is importantand in principle available in natural records such as icesheets, rocks, sediments, and the biosphere. Radiation-belt (RB) particles need to be characterized for systemdesign purposes based on archival and extreme-event in-formation, and their nowcast and forecast is importantfor planning of spacecraft special operations and maneu-vers. SEPs are highly variable and dangerous during high-intensity, large-fluence events not only for satellites, butalso for astronaut activities (which puts particular valueon the all-clear forecasts for 1-3 days). Archival and near-real time information is needed for design and anomalyresolution, while forecasts on time scales of up to a day orso are, as for the RB particles, important for planning ofspacecraft and astronaut operations. The time-scale needsfor the three different populations of energetic particles areshown separately in color-coded background bars in Figure2. The customer requirements for each infrastructure de-scribed above are based on present-day needs. We antici-pate that the requirements for GMDs and energetic parti-cles will remain in place for many years to come, perhapseven with more urgency as the power-grid reach and thepower-dependence of society grow and as we depend in-creasingly on space-based assets. For navigation and po-sitioning services the requirements appear to be alreadychanging as technologies advance: whereas satellite-only,single-frequency navigation systems are sensitive to iono-spheric electron density variability, use of dual-frequencysolutions and GNSS augmentation systems are reducingthe impact of large scale electron density variations. Themitigation of harm from ionospheric scintillation is prob-ably now the key challenge for future GNSS systems.
4. Promising opportunities and some challenges
One conclusion from the exercise with three sample im-pact chains (c.f., Appendix B) is that during recent yearsresearch in solar-terrestrial physics has advanced so much(compare Appendix C) that within the time span of next 5-10 years we anticipate far more accurate and specificforecasts of incoming solar-wind perturbations that willhave lead times from some hours to a couple of days.Such forecasts (pertaining to the heliospheric evolution ofpost-eruption solar activity prior to their arrival at Earth)would improve our capabilities to respond to the user needsdescribed in Section 3 in several ways. Therefore, we havededicated one branch in our recommendations (which werefer to as Pathway I) particularly to such research andcollaboration activities that can be coupled with the an-ticipated advancements in post-eruption forecasts.Ongoing solar missions have given us guidance on opti-mal solar surface observations to support modeling so thatimproved estimates on the CME magnetic structure andenergy content, as well as the propagation in the helio-sphere can be achieved. With this information not onlythe arrival timing of CMEs but in particular their geo-effectiveness could be provided more reliably than todayfor lead times well beyond 0.5-1 hour (which is the char-acteristic travel time for heliospheric perturbations froma sentinel placed in the solar wind upstream of Earth atthe so-called L1 point where a spacecraft can readily re-main at a nearly fixed point essentially on the Sun-Earthline). At the same time, our capabilities to monitor andmodel the near-Earth energetic particle and radiation en-vironment have advanced so much that forecasts of similarlead times can be generated to support also operations of(aero-)space assets.The improved CME forecasts would be beneficial alsofor electrical power systems because the most severe in-cidences of geomagnetic disturbances are almost alwaysassociated with magnetospheric evolution in response tothe stresses imparted by the variations in the solar wind.In many cases support would come also for the technolo-gies in communication and navigation systems, althoughthese applications would still need to tolerate the directdisturbances from solar eruptions which come in the formof light and particle bursts.Below, we first describe some promising opportunitiesin solar and heliospheric research that support the effortsfor CME forecasts with lead times well in excess of 1 hr.Harvesting these opportunities will naturally generate alsosome new challenges, not just in solar/heliospheric researchbut also in geospace research as there additional work isneeded for efficient utilization of the improved characteri-zation of solar driving. Luckily, there are some opportuni-ties also on the geospace side that we should now seize inorder to gain better understanding of certain processes inthe magnetosphere-ionosphere-thermosphere system thatcontrol the severity of SWx disturbances in the three im-pact areas. Challenges and opportunities in the researchon factors controlling large GMD and GIC are addressedafter the discussion of solar and heliospheric matters (Sec-tions 4.1 and 4.2). In Sections 4.3 and 4.4 we discuss thetasks for improved forecasts and environment specifica-tion for navigation and positioning and (aero-)space as-sets. Main points of our reasoning are presented in the13 igure 3: Identification of the top-priority needs to advance understanding of space weather to better meet the user needs, differentiated byimpact. Within each chain, letters identify opportunities for immediate advance (O), and the largest challenges (C) that need to be addressed. diagrams of Figures 2 and 3.The diagram in Figure 3 does not only address the caseof CME prediction (post-eruption), it also describes sometasks associated with the attempts to identify active areason the solar surface even before their eruption in order toachieve forecasts with lead times of several days. Althoughour current scientific understanding does not provide ade-quate support for such predictions with good enough confi-dence levels, it is good to keep also this need in the pictureas a long-term goal. The track for forecasts with lead timesbeyond a few days is described below in Section 4.5. Speci-fication of extreme conditions and solar-cycle forecasts arediscussed in Section 4.6.
Once space weather phenomena need to be forecastwith lead times that have the solar-wind driver beyondthe Sun-Earth L1 site that lies one million miles upwindfrom our planet, the observations required to make such forecasts shift to the origins of the space weather that liewithin the solar corona and the innermost domains of theheliosphere. The reason for that shift all the way towardsthe Sun is that we do not presently have the technologicalmeans to station a spacecraft on the Sun-Earth line some-where halfway the Sun and the Earth (solar sails are beingconsidered, but have yet to be demonstrated to be techno-logically feasible), nor do we have the financial resourcesto maintain a large fleet or near-Sun orbiters with at leastone always near the Sun-Earth line (although constella-tions of spacecraft have been considered for this). Giventhis situation, we conclude that forecasts beyond one hourfor solar-wind-driven magnetospheric and ionospheric vari-ability are necessarily based on observations of the domainnear the Sun and on heliospheric propagation models fromthere out to the planets, unless novel observational tech-niques or instrumentation can be developed and deployed.The timing of the impacts of heliospheric storms ongeospace is currently generally forecast based on corona-14raphic observations from which propagation speeds anddirections are estimated. Observations from the L1 sen-tinel point are nowadays provided by the LASCO coro-nagraph onboard the aging ESA/NASA SoHO mission(launched in 1996), aided by the STEREO coronagraphsand heliospheric imagers at least when in appropriate phasesof their orbits around the Sun. These observations enableestimation of arrival times that have recently become ac-curate to within a quarter to half a day, while ongoingmodeling of the background solar wind enables a roughestimate of the densities and shock strengths of the incom-ing storm. Coronagraphic imaging (now routinely in use,but generally not extending to close to the solar surface)or alternatively high-sensitivity high-altitude coronal EUVimaging (which appears technologically feasible) is there-fore critical to forecasts of solar-wind driven geomagneticdisturbances and related phenomena in the geospace ontime scales of a few hours to a few days. The potential lossof L1 coronagraphy as now performed by SoHO’s LASCOis thus a weak link in the currently available inventoryof space-weather inputs, until a replacement coronagraphis launched or until alternative means of obtaining helio-spheric observations become routinely available.When looking to forecast CME arrival times, one long-standing technique (Hewish, 1955) that is now maturingfor space weather purposes is Interplanetary Scintillation(IPS; Hewish, Scott, and Wills, 1964). This uses the scin-tillation patterns observed in the signals received from as-tronomical radio sources. This scintillation comes from thescattering of radio waves by small-scale plasma density ir-regularities propagating with the bulk solar-wind outflow.Thus, IPS provides another means of remotely sensing thesolar wind. As a complement to, say, white-light helio-spheric imagers similar to those currently aboard the STE-REO spacecraft well off the Sun-Earth line, IPS can pro-vide information on CME speeds and thus on CME arrivaltimes. When combined with modeling techniques and/orin-situ data, other parameters such as CME masses canalso be obtained, along with CME propagation directionsand arrival times (e.g., Bisi et al., 2010, and referencestherein).Another technique that is being developed to map theapproach of the CME is based on loss-cone anisotropyof ground-based muon observations: behind the shock (ifpresent) and inside the CME there is a cosmic-ray den-sity depleted region (associated with a Forbush decrease)that some times results in precursory signatures observableupstream of the shock (1 to 7 hours ahead). A detailedstudy has recently been undertaken by a group of Cana-dian experts (Trichtchenko et al., 2013) who have delivereda roadmap for development of a pre-operational system.Successful prediction of the arrival times of heliosphericperturbations is but one factor in the forecast of the mag-nitude or duration of geomagnetic perturbations. Criticalfor the forecasting of magnitude and duration of GMDs isthe knowledge of the magnetic field structure within ap-proaching solar-wind perturbations that none of the above methods can provide. Most important in determining themagnitude of the geospace response (be it immediate or de-layed) is commonly said to be the direction of the magneticfield at the leading edge, while the trailing structure affectsthe storm duration. There is, however, as yet only a poorunderstanding of the coupling of the heliospheric field intogeomagnetic activity and the data show that more charac-teristics of the solar-wind field are definitely required (e.g.,Newell et al., 2007).As a prospect for the future, a radio technique knownas Faraday rotation (FR) may offer a means of remotelysensing the heliospheric magnetic field. The FR techniqueis already used by astronomers to remotely sense galacticmagnetic fields and there are now growing efforts to applythe technique to study the heliospheric field. This is asignificant research challenge but may be within reach withcutting edge radio telescope technologies, such as LOFARand those being developed for the Square Kilometer Array(SKA).Despite some potential for the future, for the near-term, however, the only path towards successfully forecast-ing the intensity and duration of strong magnetosphericstorms, of related ionospheric current and electron den-sity variability, and of GICs beyond the next hour or so,requires that we can model the field that left the Sun.Specifically, we need to develop the means to model the in-ternal properties of the configuration of twisted magneticfield that was injected into the heliosphere in the earliestphases of a CME and the subsequent evolution of that fieldconfiguration in its interaction with the high-coronal andinner-heliospheric magnetic field into which it is thrust.Establishing the detailed geometry and strength of thecoronal magnetic field prior to eruptions (c.f. the yel-low box at the top of Figure 3), be it from strong-fieldcompact active regions or from weak-field extended quiet-Sun regions, is an area of active research. For active re-gions, the key ingredients to this are high-resolution mag-netic field observations of the solar surface layers and thenear-surface (chromospheric) layers, and high-resolutionEUV imaging in narrow thermal regimes of the overlyingcorona (flagged as “opportunities” in Figure 3). Polari-metric imaging is used to derive the vector-magnetic field,while coronal imaging provides the pathways of coronalloops that outline the magnetic field. At present, field ex-trapolations based on photospheric vector-magnetic mapsare limited to phases of slow evolution, often using theapproximation that all forces within the magnetic fieldare balanced (in the so-called non-linear force-free approx-imation in which curvature and pressure-gradient Lorentzforces cancel against each other). But even when limitingthis modeling to phases of slow evolution, models com-monly fail to reproduce the observed coronal loop geome-try, revealing the sensitivity of the field to boundary condi-tions above, below, and in the vicinity of an erupting solarregion, or to the assumed initial conditions, or both (e.g.,DeRosa et al., 2008). For weak-field regions, vector fieldsat the surface and near-surface are difficult to establish, so15-ray or EUV imaging and coronal polarimetric measure-ments sensitive to field direction (see, e.g., B¸ak-St¸e´slickaet al., 2013) may be used to constrain the magnetic fieldand, as called out as an opportunity for large telescopes(such as DKIST) polarimetric measurements sensitive tocoronal magnetic field strength may also be used in future.In general, it appears that combined measurements of thesurface magnetic field and of the coronal field as tracedby its plasma are needed to significantly advance beyondpresent-day limited and often unsuccessful field modeling(for example, Malanushenko et al., 2014).The most urgent challenge (labeled accordingly “C” inthe top yellow box in Figure 3) to be tackled to achieve re-liable forecasts of intensities and durations of geomagneticstorms on time scales of a few hours to a few days is thusthe realization of algorithms and observations needed forcoronal field modeling. These algorithms require at leastfull-Sun magnetograms combined with active-region scalevector-magnetic data and coronal high-resolution narrow-band imaging to provide crisp images of the thermal plasmaglow: that combination provides information on the so-lar surface magnetic field and, though the tracing of thecoronal field in the coronal emission patterns, also on thefield in the coronal volume above. Tracing the coronalstructures requires not only good angular resolution, butalso separation of images into narrow thermal bands sothat structures stand out well from their surroundings.Single-perspective imaging may be shown to be adequate,but binocular imaging, necessarily involving an observa-tory off the Sun-Earth line by approximately 10-20 de-grees, would substantially aid in correctly interpreting the3-dimensional coronal field structure that is otherwise seenonly in projection against the sky. Thus a second point ofview for coronal imaging substantially off the Sun-Earthline is identified as offering the potential of a big leap for-ward in space-weather forecasting on the hours to daystime scale. Surface and near-surface magnetic field mea-surements and EUV coronal imaging need to be contin-ued, because longer-term forecasts are not feasible withoutthese.
Intermediate to the initial phases of solar eruptions andthe geospace response lies the vast expanse of the sur-rounding corona coupled with the inner heliosphere (grayboxes in Figure 3): first the CMEs propagate through thesurrounding coronal field that is strong enough to mod-ify the primary direction of the initiating eruption up toa few to some ten solar radii, then they interact with thepre-existing magnetized solar wind into which the erup-tions plow on their way to the outer heliosphere. Herelies what is presently a challenge in the form of the devel-opment of a data-driven heliospheric propagation modelthat must include the properties of the magnetic field andthat is, ideally, modified by ingestion of information onthe heliospheric state by the STEREO spacecraft or bytomographic methods relying on interplanetary radio scin- tillation. The development and validation of such codesemerged as challenge in our impact tracings, that can besuccessfully dealt with after local coronal field modeling ofthe state before and after eruptions has been developed toprovide input to such models, and if the global coronal fieldis known well enough to know how the nascent CME mayhave been modified and deflected even before entering theheliosphere proper. Only once such propagation modelsare available based on the inner-boundary initial condi-tion of what has left the solar domain can the heliosphericmodel be fully tested against the observables obtained atL1 or, for the purpose of model testing and validation,at any other point within the extended heliosphere, be itcloser or further from the Sun, be it by planetary or helio-spheric missions with in-situ instrumentation.Along with the development of this heliospheric MHDmodeling capability must come the test of whether it isadequate for these few-day forecasts to measure only theEarth-facing side of the solar magnetic field or whethermore extended surface coverage of line-of-sight or vector-magnetic field is required to adequately model the foun-dation of the solar wind based on the lowest-order com-ponents of the coronal field that are determined by fieldon all sides of the Sun, including its hard-to-observe polarregions. Similarly, it should be established how impor-tant observations are of the inner heliosphere off the Sun-Earth line as data to be assimilated: are coronagraphicobservations from well off the Sun-Earth line (such asfrom around the Sun-Earth L5 or L4 regions that trailand lead Earth in its orbit around the Sun by some 40to 80 degrees where spacecraft can maintain a relativelystable position with respect to Sun and Earth) criticallyimportant, or useful as guides, or are they mostly super-fluous provided that Earth-perspective data and advancedcoronal and heliospheric modeling are available? Depend-ing on the outcome of the study of that question, coronaland inner-heliospheric imaging, such as done by the STE-REO spacecraft in some phases of their orbits, should be-come structural ingredients of the space-weather scienceand forecasting infrastructure. We note that the imple-mentation of a mission for such a perspective would alsohelp address the 180-degree ambiguity in the direction ofthe vector-magnetic component transverse to the line ofsight that currently is an intrinsic problem of even the mostadvanced solar spectro-polarimetric instrumentation. > On a par with establishing the structure of the eruptingsolar field as it begins to propagate into the heliosphere isestablishing how incoming solar-wind field structures in-teract with the magnetospheric field to drive geomagneticvariability either immediately or with delay after storingenergy in the magnetotail. L1 in-situ particle and field16easurements are critical in providing input to models fornear-term forecasts, and for validation of longer-term fore-casts of storms advancing through the heliosphere. There-fore, the continuity of L1 measurements should be ensuredso that besides the needs of operational services also theneeds from the research community are taken into account.
The coupled magnetosphere-ionosphere (MI) system re-sponds to the solar wind through processes of energy inputat the magnetopause, followed by transport and storagein the magnetosphere, and finally release of such storedmagnetic energy from the magnetospheric tail either tothe inner magnetosphere, to the ionosphere/thermosphere,or ejection into the solar wind outward through the dis-tant magnetotail. Recent discoveries from the THEMISand Cluster missions reveal the tantalizing and complexphysics of the release of such stored energy via the de-velopment and penetration of earthward propagating az-imuthally narrow channels of high speed plasma (burstybulk flows, BBF) that transport magnetic flux and embed-ded plasma earthward. On the other hand, nearer-Earthdynamics that couple these flows to the inner edge of theplasma sheet and to the flow-braking region to the iono-sphere produce large field-aligned currents and hence GICsthat are still inadequately understood. In particular, theconditions leading to, and the exact physical processes re-sponsible for, large field aligned currents (FACs) to reachthe ionosphere and drive large GICs are not known.At times, most of the magnetic energy in the magne-tosphere is stored for one to several hours, to be releasedin one drastic and intense substorm, leading to harmfulGIC effects. At other times, a large portion of the energyis transported earthward and immediately, but gradually,released through a more steady process causing quite mod-erate GIC effects. For major solar wind drivers there willalways be a resulting magnetic storm, but even such amagnetic storm is made up of several interacting and over-lapping release mechanisms including extreme convection,recurrent substorms, and recurrent plasma injections tonear-Earth region in a variety of combinations, thus mak-ing the prediction of exactly when GIC effects will occur,and exactly how intense they will be, very difficult.It has been recognized that the exact path of energydissipation in the MI system is dependent on details in thetemporal development and other characteristics of the so-lar wind driver disturbance, the pre-history of solar windconditions before the arrival of a major event, and thepre-conditioning of the ionosphere, thermosphere, plasma-sphere, radiation belts and, indeed, the magnetotail it-self. For example, the composition of low-ionization heavy(ionospheric) ions versus high-ionization low-mass (solar-wind) ions in the magnetotail depends entirely on the pre-event history of magnetospheric activity, but plays an im-portant role in the release of stored solar-wind energy inthe form of substorms, through various instabilities. Like- wise, the readiness of the ionosphere (and the magneticfield lines connecting the ionosphere to the magnetosphere)to redirect magnetospheric current through ionosphericchannels is pre-conditioned by auroral precipitation thatmodifies conductance during the substorm growth phase,when the energy stored in the magnetotail is at first onlypartially released.The challenge for understanding large GICs hence re-quires a deeper understanding of the dynamic evolution ofthe system level state of the coupled near-Earth magneto-sphere-ionosphere-thermosphere (MIT) system. Especiallyimportant is the ability to understand - and to distin-guish between - more gradual dissipation of energy andthose events associated with explosive release of storedenergy. However, the physical processes that distinguishbetween extremely rapid and more gradual energy releaseare very poorly understood. A number of important pro-cesses for energy transport and dissipation are known, buttheir inter-relationships and the pre-existing state of thesystem which is the most likely to lead to large GICs isalso not known.Almost certainly the main driver of near-Earth tail dy-namics is the conversion and release of stored magneticenergy in that region. The NASA magnetospheric multi-scale (MMS) is targeted to address details of the kineticphysics leading to fast magnetic reconnection and the re-lease of earthward flows mainly in the distant tail at 25 R E (R E is the symbol used for a distance equal to one Earthradius of 6371 km). However, the nature of the dynam-ical processes operating at the critical transition regionbetween dipole-like (closed) and tail-like (stretched) mag-netic fields (between about 6 R E and 12 R E ) remains to beproperly explored, because this region has been markedlyundersampled by previous missions. We have seen glimpsesof some of the processes that couple the tail to the iono-sphere; these indicate the importance of active MIT cou-pling in determining the overall ability of the system todrive large GICs: some times localized intensifications inauroral arcs are seen prior to substorm onset, which indi-cate changes in FACs close to the location of where thesubstorm onset occurs later. The exact character of pres-sure gradients at the earthward edge of the plasma sheetcertainly also plays an important role in this coupling. Per-haps most significant is the fact that it is currently impos-sible to distinguish between events which only result insmall-scale expansion of bright and dynamic aurorae, of-ten called pseudo-breakups, and those which lead to largeand rapid reconfigurations of the tail and full substormdevelopment with bright aurorae covering the whole mid-night sector of the auroral oval. Likely plasma sheet ki-netic plasma instabilities play an important role, but theirability to communicate with the ionosphere, in particularthe overall nature of Alfv´en wave exchange with the iono-sphere, and the balance between Ohmic dissipation andthe acceleration of field-aligned electrons, and their conse-quences for destabilizing the tail and driving large FACsand hence GICs are not known.17rom the GIC perspective, whether local instabilitiesat the inner edge of the plasma sheet precede and commu-nicate with the near-Earth neutral line, or whether globaltail reconfigurations begin with reconnection in the mid-tail is hardly relevant. The critical missing understand-ing lies in the near-Earth MI coupling processes that al-low large currents to be driven in the ionosphere, withthe consequent production of large GICs. Thus the iono-spheric ability to close major FACs in the substorm currentwedge (SCW, a current system where the magnetosphericdawn-to-dusk currents from magnetotail are diverted tothe midnight sector of the auroral ionosphere) is crucialfor the understanding significant GIC effects.In order to predict the exact route of energy dissipation,or even the timing of the onset of violent energy release af-ter a certain storage period, it is absolutely essential to un-derstand and consequently improve modeling on the prin-ciples of pre-conditioning in the coupled MIT system (c.f.“challenge” in the blue box of the left column in Figure 3).To this end, satellite- and ground-based data are requiredfrom all parts of the coupled system (flagged as “oppor-tunity” in Figure 3), both in (and below) the ionosphere,the inner magnetosphere and the magnetotail (includingthe plasma sheet where the instabilities leading to energyrelease take place), and the lobe region in which the plasmasheet is embedded, where the energy storage and releasecan be monitored. Overall, this leads to requirements formulti-point characterization of the plasma in the transitionregion between dipole and tail-like fields, together withmulti-point monitoring of the medium-altitude region (atseveral thousand kilometers) of auroral acceleration andwave reflection on conjugate field lines, with extensive sup-port from under-lying multi-instrument ground arrays ofmagnetometers, optical instruments, and HF radars, etc.Monitors of the solar wind and of incoming flows in thetail, perhaps utilizing existing assets are also required. User communities of GNSS and HF communication sys-tems have expressed needs both for nowcasts/near-termpredictions and for longer-term predictions with multi-hour to multi-day lead times (cf., background bars in Fig.2). The research and development work to fulfill theseneeds should address both rapidly evolving steep gradi-ents in the ionospheric electron density (global and re-gional scales) and processes causing ionospheric scintil-lation (local and micro scales). Forecasts of ionosphericperturbations and of upper-atmospheric variability drivenby solar flaring and CMEs rely on the advances describedabove in the two previous sections. Ionospheric pertur-bations driven by either solar flares or CMEs and associ-ated geomagnetic storm or substorm phenomena requireflare forecasts of strength and onset time of flares and ofCME arrival times and of CME field properties. Statisti-cal ionosphere models tuned with data from ground-basednetworks or low Earth orbiting (LEO) satellites can in many cases provide relatively good results for nowcasts orshort-term forecasts in regional or global scales (labeledas “opportunity” in the blue box of middle column in Fig-ure 3). However, with increasing lead times more com-prehensive physics-based modeling with data assimilationis required. We need to understand what factors controlelectron density variations during ionospheric storms, in-cluding neutral atmosphere composition temperature anddynamics, ion-neutral coupling, solar EUV, particle pre-cipitation, plasma transport, and ion chemistry (“chal-lenge” in Figure 3). Operational use of data-driven mod-els requires the availability of various actual observationdata sets covering the solar energy input including the as-sociated energy spectrum (solar spectral irradiance), theknowledge of magnetospheric key parameters such as FACsand the convection electric field, thermospheric conditionssuch as composition and winds, and current state of theionosphere such as the electron density distribution.The largest challenges in ionospheric modeling are mostprobably associated with the physics causing scintillationin radio signals. Theoretical studies addressing the growthand decay of plasma instabilities should be continued togain better understanding on processes causing scintilla-tion at high latitudes and at equatorial latitudes. As theseareas provide different background conditions for the in-stabilities, for example due to different internal magneticfield orientation and solar forcing, there is no single generalapproach to address them both.Ground-based observations of the Earth’s upper atmo-sphere have been expanded extensively in the last decade,especially with new coherent and incoherent radars, newionosondes, new all-sky photometers, and new digital im-agers from several different generations, mainly set closeand around the magnetic equator and at high latitudes toobserve and study plasma bubbles and auroral instabilitiesand their driving mechanisms. Despite such increases inthe observations of these space weather phenomena, thereare still scientific issues that are not solved, including, forexample, the day-to-day forecast of plasma bubbles as wellas teh day-to-day neutral wind that drives their develop-ment.
Near-real time solar-wind conditions are the controllingfactors for the near-Earth energetic particle population,but the preceding evolution of that system is also critical;the result is an energetic particle environment in whichthe outer radiation belts are dominated by locally accel-erated particles. For example, efficient energetic particleproduction mechanisms appear to need a seed populationof energetic electrons. Relativistic electrons enhancementsare an important space weather factor with a strong influ-ence on satellite electronics. Around half of all magneticstorms are followed by a corresponding enhancement of rel-ativistic electron fluxes. However, GCRs- and SEPs canalso penetrate into the terrestrial magnetosphere. SEPs18an originate either by direct acceleration in the corona,which can result in very prompt fluxes in the case of directinterplanetary linkage, or by acceleration at interplanetaryshocks, from where SEPs can propagate towards Earththrough direct magnetic-field linkage or by being carriedwithin the CME so that their SEP populations may even-tually pass by, and then temporarily envelop, Earth.SEPs and GCRs originate from within the solar sys-tem and beyond, in the Galaxy, respectively, and propa-gate to the Earth’s orbit. The geomagnetic field controlsthe penetration of SEP and GCR particles into the nearEarth environment, such that lower energy particles pen-etrate only into polar regions (for example, energies belowabout 1GeV penetrate only poleward of about 55 degreesmagnetic latitude), but progressively lower latitudes arepenetrated as energies increase (an energy approaching 20GeV is required to penetrate to the equator; Beer, 2010).Thus the high-energy GCR particles penetrate much moredeeply than do most solar particles; only rarely do SEPshave sufficient energy to reach deep into the equatorial re-gions. The latitude to which particles penetrate is knownas the geomagnetic cutoff and depends on both particleproperties and on the geomagnetic field strength. Thisgeomagnetic cutoff filtering is important for satellite andaviation operators, as it controls the particle properties towhich their systems are exposed.GCRs and very high energy SEPs that penetrate deepinto the atmosphere collide with atmospheric species toproduce neutrons, muons and other secondary particles.Ground-level and aircraft measurements of these secondaryparticles give useful insights into the very high-energy partof SEP energy spectra. However, the transport of this par-ticle radiation through the magnetosphere and atmosphereneeds to be better understood; measurements, especiallyon aircraft, are needed to challenge and stimulate GCRand SEP radiation transport models.Trapped energetic particles in the inner magnetosphereform radiation belts. The inner proton belt is fairly sta-ble, but the outer radiation belt comprises a highly vari-able population of relativistic electrons - with fluxes of-ten increasing abruptly but generally decaying only slowly.Solar-wind changes produce changes to trapped-particletransport, acceleration, and loss. However, the pre-existingmagnetospheric state is also important and therefore manyof the challenges and opportunities listed above for theGMD/GIC case are relevant also for improved understand-ing on SWx effects in the radiation environment. Contin-uous solar-wind and solar observations are needed to pre-dict magnetospheric disturbances and corresponding auro-ral precipitations, field-aligned current variations, trappedparticle variations and any SEP penetration.Intensification of magnetospheric convection during stormtimes, local particle acceleration due to substorm activity,and resonant wave-particle interaction are the main fun-damental processes that cause particle energization andloss. However, the details of the mechanisms which may beable to contribute to these processes - including a variety of wave particle interactions, enhanced convection and ra-dial diffusion - remain a subject for active research. Whileprogress has been made in the theoretical understanding ofthese competing processes, there is as yet no consensus onwhich of these will be significant in particular situations,and no real predictive methods that can give precise fluxesat different local and universal times. There is therefore apressing need to confront theoretical models with detailedmeasurements in order to resolve these shortfalls (see righthand column in Figure 3). Data incorporation is neededto take into account local plasma processes affecting themagnetic field variations and corresponding particle accel-erations, losses etc. As much as possible data are neededfor nowcasting of energetic particle fluxes. GEO, LEO,MEO, GTO data are very important. Data calibrationis needed to provide the correct result. It is essential forsatellite operators to know the past, current and futurecondition of the space environment around their satellites,especially in case of satellite anomaly and/or before criti-cal operation.Finally, there are short-lived populations of ring-currentparticles produced by substorms and enhanced magneto-spheric convection. Currently, our understanding of sub-storm onset is evolving rapidly, in particular with respectto local dipolarization structures. However, we are still along way from an ability to predict precise events. Cur-rent spacecraft measurement configurations are probablynot sufficient to make accurate predictions. Because theseeffects are the major contributor to spacecraft failures dueto charging, it is essential that current investigations aremaintained and extended (reflected as highest-priority op-portunity in Fig. 3). Magnetic field models (empirical,numerical) with particle tracing codes are needed to now-cast/forecast particle distribution. They require current orpredicted solar-wind information for nowcasting/forecasting.Data sources are solar wind monitoring data and solar UVimages, models of solar wind propagation from the Sun.
Forecasts of substantial space weather events that ex-tend beyond a few days require, by definition, forecasts ofenergetic events well before they occur on the Sun. Thisrequires advancing our understanding of the storage andinstability mechanisms for the solar magnetic field. Manyof the issues involved in that will be addressed by the sci-ence described in Section 4.1.1, including knowledge of the3D structure of the field and estimations of energy and he-licity budgets. With the advancement of that understand-ing will also come the ability to experiment with the fieldconfigurations to deepen insights into the conditions un-der which such fields become unstable for flares and CMEs(see Appendix D for more discussion and a listing of re-quirements). Support of the research described in Section4.1 will thus also support pre-event forecasts for that reachsome hours to a day before the event occurs on the sun.For forecasts of CME arrivals well beyond the few daysthat it takes to travel through the heliosphere to reach19arth, this means that forecasts need to be made even be-fore the source regions of potentially geo-effective CMEshave rotated from near the east limb towards the Earth-perspective central meridian. In contrast, prompt SEPstorms around Earth often originate from solar regionsthat have rotated several days past central-meridian pas-sage towards the west limb. This adds some complicationin that the magnetic maps of such regions suffer from per-spective changes, but that can be dealt with as long as theregions are not too close to the limb (i.e., within about4-5 days of central meridian passage). What is a muchlarger challenge here is that in many cases such longer-term forecasts for active regions need to be made evenbefore much of the involved field has emerged onto thesolar surface. It appears that field configurations leadingto the most intense space weather originating in active-region flares and eruptions form and decay within a dayor two of the emergence of twisted bundles of magneticflux or the shearing by convective flows of such bundles.Once emerged and interacting with the pre-existing field,the available non-potential energy can be processed eitherthrough a rapid conversion in a flare/eruption or can begradually dissipated, likely contributing somehow to thethermal energy of the solar atmosphere (therein findingan intriguing analogy with the options for magnetosphericrelaxation discussed above).The successful quantification of the subsurface mag-netic field that will be involved in possible solar eruptionupon emergence by helioseismic techniques currently liesbeyond our capabilities, and even beyond a proof of prin-ciple in advanced helioseismic magneto-convective simu-lations. It thus appears premature to invest in instru-ment opportunities solely for helioseismic investigations ofthe eastern/leading solar limb for the purpose of explor-ing the potential of, say, five-day pre-event forecasts. Wedo recommend, however, continued support for the de-velopment and testing of helioseismic methods that mayreveal how we can detect and characterize magnetic fluxbundles about to emerge onto the solar surface a day ormore ahead of time. The background solar-wind sectorstructure involved in recurring geomagnetic perturbationsis driven mostly by the rotation of the largest-scale fieldstructures on the Sun. The forecasts of the sector structureand the non-CME-related patters of fast and slow solarwind streams will benefit from the advanced knowledge ofthe global solar field and the associated heliospheric mod-eling described in Section 4.1.2. The more extensive theobservational magnetograph coverage is of the solar active-region belt, the better multi-day forecasts will become forthe overall solar wind stream and sector structures. Asthe requirements for this overlap with those articulated inSection 4.1.2, we do not repeat these here.
Quantitative knowledge of low-frequency, high-impactspace weather cannot be derived by observing the Sun- Earth system in modern times, simply because too fewof the severe events have occurred, and the most extrememay not yet have been observed at all as yet. Rather,we must gather data that tell us about solar activity overmany centuries in order to reach useful, reliable conclu-sions about events that happen once per century or onceper millennium. For energetic particle storms and theGCR background, such information can be obtained ex-tending over tens of millennia by combining terrestrial andlunar radionuclide studies based on rocks, ice cores, andbiosphere-modulated radio-nuclide records (including, forexample, carbon-14). To quantify the frequency spectrumfor solar flares we can look at the multitude of Sun-likestars accessible by nighttime ground-based or space-basedastronomical telescopes, as demonstrated by, for example,NASA’s Kepler mission and by X-ray and EUV space as-trophysics missions (Schrijver and Beer, 2014). Currentevidence suggests that even for our aging Sun events thatare tens of times more intense than the most energetic so-lar ones observed during the space era may occur on timescales of once per century to millennium. We recommendthat the solar-stellar links be strengthened to better quan-tify the probability distribution of the most intense butinfrequent solar flares by using archival data on Sun-likestars already available and by supporting possible futureopportunities to add to that statistical information.As to energetic particle storms, it is prudent to makethe moderate investment needed to harvest the radio-nuclideinformation stored in ice, biosphere, and the rocks broughtback from the Moon during the Apollo era. Parts of thisoverall project involve improving our knowledge of the dis-tribution of energies over particle spectra and photon spec-tra, as well as understanding how terrestrial particle spec-tra can be combined with photon spectra to understandhow solar/stellar flares and particle storms are related forthe most intense and dangerous events.An entirely different class of problems is to be ad-dressed for multi-year to multi-decade variability that isdriven by the general patterns of the solar cycle. Informa-tion on past solar cycles is, of course, coming from studiesof sunspot patterns, of radionuclide studies associated withGCR modulations by the large-scale structure of the solarwind, and even from studies of potential climate impactsin the pre-industrial era on time scales from decades tomillennia. The inter-disciplinary work that is required forthat should be stimulated as an aid to environmental spec-ification for designs of long-lasting infrastructures, both inspace and on the ground. Multi-year to multi-decade fore-casts, on the other hand, need to see investments in un-derstanding the solar dynamo. The observational require-ments for this involve continued observations of the solarmagnetic field and of the flows involved in transporting itacross the solar surface and throughout its interior. Here,continued magnetic observations as required for the sciencedescribed in Section 4.1 supports the need for surface cov-erage. Continued helioseismic observations to study thevariability of deep flow patterns involved in the dynamo20re needed in addition. Moreover, strengthening ties withthe astrophysical community looking into dynamo activityin Sun-like stars is needed.Involvement in the study of habitability of exoplanets isa natural stimulus for both the extreme event knowledgeand improved dynamo understanding because exoplanetspace weather is a dynamic emerging field that can bene-fit from Sun-Earth connections knowledge as much as itsdiscoveries can inform us about extremes and long-termtrends in space weather in our own planetary system. Weencourage stimulus of these research fields, but as these lieat the fringe of our central charge, we do not at presentmake any explicit recommendations for investments in re-search and its observational infrastructure, other than em-phasizing that funding agencies would be well advised touse the synergy between solar and stellar research and be-tween planetary-system and exoplanet habitability to im-prove our abilities to specify and predict extreme space-weather conditions and long-term trends.
5. General recommendations
With so much yet to understand, and so much space(literally) to cover observationally and in computer mod-els, the needs readily outweigh the means we can expectto have at our disposal. A major effort of the roadmapteam therefore focused on identifying where investmentswould make the largest impact in advancing our scientificinsights to best meet the needs of the space weather users.We base that analysis on these identified primary needs: • For the research community: Comprehensive knowl-edge of conditions throughout the Sun-Earth systemin the past based on models guided by observations,and the understanding of the physical mechanismsinvolved in determining these conditions. • For the space-weather customer community: Knowl-edge of historical and recent conditions and knowl-edge of current conditions and forecasts for com-ing hours to days, and specification of extreme con-ditions in geospace and throughout interplanetaryspace. Different user communities require differenttypes of data and distinct levels of accuracy andspecificity.From these follow primary requirements: • Comprehensive, affordable, sustained observationalcoverage of the space weather system from Sun tosociety; • Data archiving, sharing, access, and standardizationbetween the various researcher and customer com-munities; • Advanced data-driven and experimental models astools for analysis, interpretation, and visualizationof events and their spatio-temporal context, and forforecasting/specification; • Interaction and coordination between national, re-gional, and international researcher, user, and agencycommunities for research guidance, prioritization, im-pact assessment, and funding; • Education of researchers, customers, and general pub-lic.These requirements need to be addressed in the contextof a changing paradigm in the science of space weather:whereas many studies to date tend to focus on what theyrefer to as “space weather events”, there is a rapidly grow-ing realization that in fact significantly longer time se-quences need to be studied because there appears to bean important if not crucial impact of what is either de-scribed as hysteresis or as pre-conditioning in the system.This is now recognized to reach from the solar environ-ment to deep within geospace: solar active regions emergepreferentially in locations where other such emergence hasoccurred before; nascent CMEs often plow through highcoronal field that is still relaxing from preceding eruptions;interplanetary solar-wind structures are often mergers ofmultiple sequential CMEs; geo-effectiveness of CMEs isdependent on pre-conditioning of the magnetosphere byactivity over the preceding days; substorms appear to re-lease stresses in the magnetotail built-up over some pe-riod of time; preceding conditions in the ionosphere controlthe timing and intensity of substorm onsets; and so forth.Consequently, there must be a shift away from the study ofshort time intervals that attempt to study space weatheras if pre-conditioning were unimportant, moving towardsthe analysis of multi-day windows of space weather thatmakes allowance for significant effects of hysteresis in theSun-Earth system and its components.The impact tracings discussed in the preceding section,and detailed in Appendices B, D and E, lead us to formu-late the following general priorities for actions that guideus to the detailed implementation suggestions for devel-opments of new observational, computational, and theo-retical capabilities that are discussed in the subsequentsection. We begin with a concise listing of the prioritiesfor three distinct target audiences, followed in the nextthree subsections (5.1, 5.2, and 5.3) by a point-by-pointexpansion into the types of actions to be considered orimplemented.
Research: observational, computational, and theoretical needs:. Advance the international Sun-Earth systemobservatory along with models to improve fore-casts based on understanding of real-worldevents through the development of innovativeapproaches to data incorporation, includingdata-driving, data assimilation, and ensemblemodeling.
The focus needs to be on developingmodels for the Sun-Earth system, at first as researchtools focusing on actual conditions and later to tran-sition to forecast tools, making use of the existing21ystem before components are lost as instrumenta-tion fails or is discontinued.2.
Understand space weather origins at the Sunand their propagation in the heliosphere, ini-tially prioritizing post-event solar eruption mod-eling to develop multi-day forecasts of geo-magnetic disturbance times and strengths:
Ad-vance the ability to forecast solar inputs into geo-space at least 12 hrs ahead based on observationsand models of their solar drivers as input into he-liospheric propagation models.3.
Understand the factors that control the gen-eration of geomagnetically-induced currents(GICs) and of harsh radiation in geospace, in-volving the coupling of the solar wind distur-bances to internal magnetospheric processesand the ionosphere below:
Advance the abilityto forecast the response of the geospace system todriving by solar-wind variability.4.
Develop comprehensive space environment spec-ification:
Create a reference specification of condi-tions and their likelihoods for the local cosmos.
Teaming of research and users: coordinated collaborativeenvironment:. I Quantify the vulnerability of technological in-frastructure to space weather phenomena jointlywith stakeholder groups.II
Build test beds in which coordinated observ-ing supports model development:
Stimulate thedevelopment of (a) state-of-the-art environments fornumerical experimentation and (b) focus areas ofcomprehensive observational coverage as tools to ad-vance understanding of the Sun-Earth system, to val-idate forecast tools, and to guide requirements foroperational forecasting.III
Standardize (meta-)data and product metricsand harmonize access to data and model archives:
Define standards for observational and model dataproducts, for data dissemination, for archive access,for inter-calibration, and for metrics. Define datasets needed to test physical models and forecast sys-tems.IV
Optimize observational coverage:
Increase cov-erage of the Sun-Earth system by combining obser-vations with data-driven models, by optimizing useof existing ground-based and space-based resources,by developing affordable new instrumentation andexploring alternative techniques, and through part-nerships between scientific and industry sectors.
Collaboration between agencies and communities:. A Implement an open space-weather data andinformation policy:
Promote data sharing through(1) open data policies, (2) trusted-broker environ-ments for access to space-weather impact data, and(3) partnerships with the private sector. B
Identify, develop, and provide access to qual-ity education and information materials forall stakeholder groups:
Collect and develop edu-cational materials on space weather and its societalimpacts, and create and support resource hubs foraccess to these materials, and similarly for space-weather related data and data products. Stimulatecollaboration among universities in order to promotehomogenized space-weather education as part of thecurricula.C
Execute an international, inter-agency assess-ment of the state of the field to evolve pri-orities subject to scientific, technological, anduser-base developments to guide internationalcoordination:
Identify an organizational structure(possibly the COSPAR/ILWS combination leadingto this roadmap) to perform comprehensive assess-ments of the state of the science of space weatheron a 5-year basis to ensure sustained developmentand availability of high-priority data, models, andresearch infrastructure. This activity can be a foun-dation to align the plans of research agencies aroundthe world if, as for example for this roadmap, agencyrepresentatives are engaged in the discussions.D
Develop settings to transition research toolsto operations.
Establish collaborative activities tohost, evaluate, and compare numerical models (look-ing at the Community Coordinated Modeling Cen-ter [CCMC] and the Joint Center for Satellite DataAssimilation [JCSDA] as examples, setup, staffedappropriately from research and user communities)and to assess quantitatively their skill at forecast-ing/specifying parameters of high operational value.Determine the suitability of research models for usein a space weather service center. Foster continuousimprovement in operational capabilities by identify-ing the performance gaps in research and operationalmodels and by encouraging development in high pri-ority areas.E
Partner with the weather and solid-Earth com-munities to share infrastructure and lessonslearned.
To improve understanding of the couplingsbetween weather and space-weather variability andto quantify potential climate impacts by effects re-lated to space weather. Another type of partnershiphere involves the transfer of knowledge and “lessonslearned” from the climate/weather communities ontechniques for data-driven assimilative ensemble mod-eling and on the development of forecasts and theirstandards based on that. For the solid-Earth com-munity: translation of geomagnetic variability intoelectric fields involved in GICs.The above “General Recommendations” (listed in pri-ority order within each target group) as formulated by thisroadmap team align with many found in other studies andworkshops (e.g., Committee on Progress and Priorities of22.S. Weather Research and Research-to-Operations Ac-tivities, 2010; American Meteorological Society, 2011; ECJoint Research Center by Krausmann, 2011; Committeeon a Decadal Strategy for Solar and Space Physics, 2012;United Nations Committee on the Peaceful Uses of OuterSpace, 2013). This roadmap advances from the generaland system-wide recommendations in those earlier reportsby including a rationale for the prioritization of invest-ments for the worldwide community subject to limited re-sources.
The Sun-Earth system is currently observed by an un-precedented array of ground- and space-based instrumentsthat together provide a comprehensive view, but one thatis so sparse that the loss (through failure or termination)of any one key asset would have a substantial impact onthe overall study of space weather phenomena. Note thatour recommendation on access to the data from this sys-tem observatory is listed above as item A, and expandedupon in Section 5.3, item A.
Recommendation:
Funding agencies should place thecontinuation of existing observational capabilities withinthe context of the overall Sun-Earth System observatoryas a very high priority when reviewing instrumentationfor continued funding: the value of any one observablewithin the entire set of Sun-Earth observables should sig-nificantly outweigh whether the instrument has met itsown scientific goals or whether it, by itself only, meritscontinuation based on its standalone scientific potential.The prioritization of international assets should be takenfrom a community-based assessment, such as this roadmapand its recommended successors. Of particular impor-tance to be continued are: Earth-perspective magneticmaps and X/EUV images, solar spectral irradiance mon-itors (including X-rays to UV and radio), coronagraphy(ideally from multiple perspectives), solar radio imaging,in-situ (near-)L1 measurements of the solar wind plasma(including composition) and its embedded field and ener-getic particles, ground-based sensors for geomagnetic fieldand ionospheric electron density variability and neutral-atmosphere dynamics, LEO to GEO electron and ion pop-ulations, in-situ magnetospheric magnetic and electric fields,and geomagnetic field measurements, space-based auroralimagers, and energetic-particle sensors (including ground-based neutron monitors) where available throughout theinner heliosphere.Most space weather models, whether for research or forforecasts, currently rely on snapshots or trends in observ-ables, or on extrapolations from one location to model con- ditions in another, with little or no direct guidance by ob-servations of evolving conditions at the boundaries and inthe interior of the modeled volume. This is in part becausedata incorporation strategies are only in their infancy, andin part because data types and model algorithms are notoptimized for assimilation processes.
Recommendation:
Funding agencies should imme-diately begin to give preference to modeling projects thatuse, or are specifically designed to eventually enable, director indirect guidance by observational data. Funding agen-cies should require efficient online access to relevant datasets by standardization of interfaces and by the creation ofinterface hubs and tools that transform data sets into stan-dard formats that are compatible with common practicesin different disciplines. Each agency can focus on its owndata, but agencies should coordinate in the developmentof data standards and standardized interface, emphasizingthe importance of near-real-time data availability. TheILWS program partnership can be a coordinating hub inthis process.
2) Understand space weather origins at the Sun andtheir propagation in the heliosphere, initially prioritizingpost-event solar eruption modeling to develop multi-dayforecasts of geomagnetic disturbance times and strengths,after propagation through the heliosphere.
This priority is associated with two scientific focus ar-eas. The first is the need to enable a much-improved quan-tification of the non-potential magnetic field of source re-gions of solar activity pre- and post-eruption, for whichwe propose local-area binocular imaging as well as high-resolution comprehensive imaging that includes vector-mag-netography of the solar surface and chromosphere on thescale of the erupting region. The second involves advancedmodeling capabilities for the coupling from the localizedsource-region corona into the overall heliosphere, and thecomputation of the propagation of plasma and embeddedmagnetic field through the heliosphere towards geospace,for which we propose increased coverage of the solar sur-face magnetic field, and advanced modeling capabilities forthe global coronal and inner-heliospheric dynamic mag-netic field and solar-wind plasma. The specific recom-mendations associated with this research focus area arepresented in detail in Sections 6, 7a and 7c.
3) Understand the factors that control the generation ofgeomagnetically-induced currents (GICs) and of harsh ra-diation in geospace, involving the coupling of the solar winddisturbances to internal magnetospheric processes and theionosphere below.
This priority is associated with several recommenda-tions. The first involves satellite coverage in the domainbetween the dipole-tail transition region at the inner edgeof the plasma sheet and in the near-Earth domain of themagnetospheric field (at the auroral acceleration region atseveral 1000 km altitude) to probe, along essentially thesame magnetic field lines, the processes that throttle be-ginning magnetotail activity and that determine if that23ctivity may develop into a magnetospheric (sub-)stormand associated intense GICs or not. The second recom-mendation for this priority emphasizes the need for co-ordinated ground-based and space-based networks of in-strumentation, and the development of “testbed” locationswhere dense observational coverage provides informationon key distinct environments for geomagnetic and iono-spheric electron density variability (specifically for the au-roral zone and the near-equatorial region). The two com-plementary sets of recommendations are described in de-tail below in Sections 6, 7b, and 7d-f.In addition to these recommendations regarding mag-netospheric and ionospheric processes driven from outsideand within the M-I system, there are the processes thatsubject the ionosphere to forcing by the neutral terres-trial atmosphere for which we articulate this specific addi-tional recommendation: Recommendation: Funding agen-cies should place the continuation of existing observationalcapabilities within the context of the upper atmosphere aswell as the computational capability that leads to its un-derstanding for the scientific and operational purposes ata high priority. It also recommended that the coverage ofthe ground-based instrumentation be coordinated in thedevelopment of new instrumentation, including integra-tion of ground- and/or space-based data systems. Also,it is recommended to include that lower-atmospheric in-formation into data-driven modeling capabilities for thenear-real-time ionospheric state. Additionally, the scien-tific community should pursue a general consensus on theunderlying physics with the processes associated with ra-dio scintillation, in particular about the coupling betweenneutral atmospheric winds and waves, and development ofthe plasma turbulence that leads to the bubble formationat equatorial latitudes
4) Develop a comprehensive space environment specifi-cation:
With robotic and manned spacecraft becoming evermore frequent and venturing into new orbits around Earthand the solar system, it is important that we establish indetail the conditions to be encountered by these space-craft prior to their design so that they can be built tosurvive space weather storms and be resilient to recoverfrom such storms. Similarly, design criteria for technolog-ical infrastructures used on Earth need to be set so thatthey can resist, survive, and recover from effects of spacestorms. This requires information on space weather condi-tions that may be encountered during the lifetime of suchspacecraft and ground-based systems.
Recommendation:
We recommend for the near termthat detailed specifications be compiled of all relevant space-weather phenomena (following the recommendation for anopen-data policy formulated below) that may be encoun-tered wherever human technologies are, or likely will be,deployed; this includes properties of particle storms, so-lar irradiance variability, and geomagnetic variability, fromlow-level generally present backgrounds to rare, extreme, impulsive events. We recommend for the near- and mid-term that research funding be allocated to this effort thatincludes studies of radionuclides in the terrestrial biosphereand cryosphere, as well as in lunar and terrestrial litho-spheres; that analogies between Sun and Sun-like stars beexplored; and that advanced modeling be deployed to un-derstand extremes in geomagnetic, heliospheric, and solarconditions.
Recommendation:
We recommend for the near termthat the space weather community engage with researchagencies responsible for the study of economic and so-cietal developments and encourage them to explore andsupport research to quantify the impact of space weatherphenomena on societal technologies. Where these agen-cies are separate from space organizations, the communityshould encourage them to work with space organizations.In all cases, the support for research on impacts shouldenable and stimulate the trans-disciplinary research thatis required, and should also encourage a data-sharing envi-ronment in which industries are given confidence that theycan share information on space-weather impacts withoutconcerns for their commercial competitiveness or their po-tential liabilities. To achieve this, we recommend that allresearch proposals on impact studies should be stronglyencouraged to combine the research and user communi-ties and their joint expertise and data. We also recom-mend that a trusted-broker environment be given shapeby a group that involves stakeholders from government,academia, as well as industry. The community should alsoencourage international coordination of impact studies.
II. Build test beds in which coordinated observing sup-ports model development.
Some domains within the Sun-Earth system are coveredbetter by observations than others. For example, there aresites for ionospheric research that are favorably locatedand well equipped with particularly valuable or state-of-the-art instrumentation. Coordination between the vari- ous space- and ground-based solar observatories in observ-ing campaigns of particularly active space-weather sourceregions on the solar surface offer another opportunity for a“laboratory” with extensive empirical coverage of regionsof interest. Test-bed data could be used to learn whichtypes of observations are most suitable for data incorpora-tion in modeling and which resolutions in space and timewould be suitable compromises when considering both in-strument maintenance costs and additional gain from dataingestion.
Recommendation:
We recommend for the mid-termthat international resources be optimally pooled, particu-larly in settings where significant investments have alreadybeen made: ground-based observatories of the ITM systemin Jicamarca and around EISCAT appear well suited forfocused further development; international coordinationbetween solar observatories (in space and on the ground)should be mandated by funding agencies for a fraction ofthe total observing time available; data assimilation effortswith the continuously developing models should be sup-ported by access to large-scale computer facilities (e.g., theIBM ExaScience Lab in Belgium) with national, EU, NSFor space agency funding. Results from test runs should bepublished in platforms that enable community based codedevelopment and testing (e.g., NASA CCMC and ESAvirtual space weather modeling center) in order to harvesttheoretical and computational skills from the entire SWxcommunity.To make a step change in the international co-ordination,and delivery, of space weather observing systems we mustincrease the engagement of scientists working with thisinstrumentation with modelers, operators of space-basedsensors, and other consumers of space weather data. Thatshould be aimed to ensure the optimum interaction be-tween the collected data and state-of-the-art internationalmodels, and the synthesis of these data and model resultsinto, first, research tools and, later, into operational toolswhose outputs can be made available to the applicationsand technology community. In order to improve the situ-ation, the geospace observing system needs a more formalinternational structure to deliver its full scientific poten-tial.
Recommendation:
We recommend establishing a globalprogram at inter-agency level for coordination of spaceweather observing systems, perhaps similar to coordina-tion of space exploration activities.
III. Standardize (meta-)data and product metrics andharmonize access to data and model archives:
Making efficient use of data, and even finding data thatare in principle useful in advancing the science of spaceweather require adequate standardization in data formatsand access protocols to on-line data archives. Knowledgeof quality of data products and of space weather applica-tions requires development of data product standards.
Recommendation:
We recommend that funding agen-cies require development of data archiving, data search,25nd data access plans as part of observatory/instrumentoperations support, retro-actively where needed; this shouldinclude standardization of data formats and of data re-trieval methods (i.e., web and application interfaces). Werecommend that funding agencies coordinate any neededreprocessing of historical datasets to make them gener-ally available in a standard way. We recommend thata study be commissioned, possibly under the auspices ofWMO, COSPAR, and/or ILWS, to address issues relatedto the long-term preservation of data archives. We alsorecommend that agencies resolve issues that hamper useof science data or products that are not at all available forcommercial use (such as the Dst index) in an environmentwhere tailored space weather surveces may increasingly beprovided by commercial entities. Finally, we recommendthat standard metrics are developed for data product qual-ity and applications quality.
IV. Optimize observational coverage:
The space from Sun to Earth is vast and poorly coveredby observatories. Part of that problem is limited access toexisting information - such as ionospheric information thatis available to, but not effectively shared by, the GNSSnavigational service sector - while another part is relatedto the cost of instrumentation, particularly in space. Thehigh cost of space missions percolates into several concerns:high costs lead to low frequency of deployment which (a)causes instrumentation to be deployed one or two decadesbehind the technological frontier, and (b) slows or pre-cludes filling of gaps in the vast space to be covered andin terms of observables that are accessible. The science ofthe Sun-Earth connections that underlie space weather isparticularly affected by this problem because the systemto be observed is vast and the number of instruments verysmall in comparison. But precisely because of that, it isa particularly suitable area for which this issue should beaddressed because any new instrumentation is deployed asan augmentation to an existing Sun-Earth system obser-vatory so that even relatively small new ground-based ob-servatories or space missions can significantly strengthenthe overall system observatory as it advances that into ascientifically much more capable state.
Recommendation:
We recommend that research or-ganizations and industry sectors partner to optimize useof already available data related to space weather impacts;central government organizations (such as OSTP in theUS) should play a leading role in fostering this sharing ofresources. Recommendation: We recommend that spaceagencies urgently seek to lower the costs to achieve theirscience goals by (a) emphasizing partnerships and effec-tive use of small opportunities within the context of theSun-Earth system observatory, (b) by developing infras-tructures and rule sets that enable lower-cost access tospace in the mid- and long-term, and (c) by implement-ing sustained diversification of their research fleets withsmall niche satellites and clusters of smallsats (perhapseven microsats surrounding a larger mother ship with cen- tral coordination and communication abilities), all to en-able more frequent insertion of new observatories (stan-dalone and as hosted payloads) that can better utilizestate-of-the-art technologies, where possible in “off-the-shelf”¨configurations. In working towards these goals, re-search agencies should take care to maintain the most im-portant observational capabilities in the currently operat-ing distributed Sun-Earth system observatory, ideally incoordination with, and in consultation with, the researchcommunity to most efficiently advance the system obser-vatory’s capabilities.As part of this recommendation, we note also that ef-forts should be made to increase the availability of ground-based data on the geomagnetic field and on the state ofthe ionosphere with high timeliness. This can be accom-plished by: (i) considering the deployment of magnetome-ters and other low cost ionospheric instrumentation (radiowave based probing techniques) in regions with limitedcoverage; (ii) utilizing the WMO data infrastructure todisseminate data from existing instrumentation; and (iii)working with providers of proprietary data to allow theirdata to be used in space weather products. We also em-phasize the opportunity to expand ground-based coverageby using relatively small facilities that enable emergingcountries to become involved in space weather research.
Open access to relevant space weather data will stimu-late research by enabling innovative uses of observations ofthe Sun-Earth system, of modeling data relevant to thatsystem, of impact data for space weather phenomena, andof societal consequences of such phenomena. An open datapolicy is already agreed upon in the G8 “Open Data Char-ter” (2013) between governments, but we argue for a wideradoption of that charter beyond the G8 nations, and to ex-plicitly define “open data” to mean that data should beopen to all users as soon as such data is archived for useany research group. Funding agencies supporting estab-lishment and maintenance of SWx infrastructures shouldfavor such initiatives that follow this open data policy. Ageneral open data policy, supported by an infrastructure ofvirtual observatories, will stimulate research in general, inparticular by enabling the utilization of ancillary and ad-jacent data to observations being analyzed by a researchgroup. Recommendation: We recommend that observa-tional data pertinent to space weather be made publiclyaccessible as soon as such data is calibrated adequatelyfor scientific use. Data sets obtained with routine instru-ment setups or for monitoring or survey purposes should bemandatorily archived and opened up for immediate inter-net access without proprietary periods starting as soon asdata are archived and provisionally calibrated and charac-terized by meta-data. We also recommend that data shar-ing be a formalized part of observatory planning, funding,26nd operating, including sharing between space-based andground-based observatories and instrumentation.
Recommendation:
Agencies that fund instrumentoperations should provide sufficient resources to enable ef-ficient open data access - perhaps through a mix of directfunding to instrument operators to generate and store dataproducts and their metadata, and funding for data infras-tructures that catalog and provide access to these prod-ucts. Virtual observatories and/or general software (suchas exists for SolarSoft IDL) should be sustained and de-veloped to ease data identification and retrieval from thearchives. Recommendation: We recommend that a similaropen-data policy for assimilation model data be developedand implemented where practical in the mid-term.
B. Identify develop, and provide access to quality educa-tion and information materials for all stakeholder groups:
There is huge public interest in space weather and itsimpact on humankind, in part because it is a spectacu-lar natural phenomenon, and in part because it is a riskthat appeals to the human love of scare tales. As a resultthe internet provides access to a vast and ever-growingmultitude of web sites and web pages related to the topicof space weather (see Figure 1). However, this informa-tion is of very variable quality and many web pages con-tain significant factual errors in both the science and theimpact of space weather. These errors frequently propa-gate into other web sites, into the media, and even intothe discussion of space weather by policy makers. There-fore, it is critically important to guide all stakeholders ofspace weather towards high-quality information on spaceweather; these stakeholders include policy-makers, regu-lators, educators, engineers, system operators, scientists,and many more. The wider scientific community is also acritical target, especially the closely related scientific areassuch as plasma physics, radiation physics, planetary explo-ration, and astrophysics. Furthermore, the increasing pub-lic interest on space weather is stimulating an increased fo-cus on Sun-Earth connections as part of university level ed-ucation. In this relatively young and specialized researchdiscipline, the level and focus of education may vary be-tween different universities, which can cause complicationsin student exchange or in recruitment of early career sci-entists.
Recommendation:
We recommend the developmentof an international structure that can coordinate a globaleffort to identify and/or develop high-quality informationthat addresses the needs of all types of stakeholders inspace weather, and does so in a way that facilitates cus-tomization of information to local (national/regional) cir-cumstances, especially targeting diversification towards cul-ture and language. To deliver this we recommend a struc-ture that engages the leading disseminators of space weatherknowledge in each country, including space-weather sci-ence experts who have a good appreciation of how the sci-ence of space weather links into impacts on practical sys-tems of local importance, and of how their national struc- tures handle both the science and the impacts of spaceweather. A key goal is to link with the most suitable na-tional structures, recognizing these will vary considerablyfrom country to country. The structure should also en-compass dissemination activities in international bodies,including ISES, WMO, UN/COPUOS, ESA, IUGG, IAU,COSPAR, EGU and AOGS.In the very near-term we recommend that a workinggroup (a) carry out a survey to identify and engage thenational experts and structures most active in develop-ing and disseminating high-quality information, and then(b) propose an international structure that can coordi-nate their efforts on the tasks shown below. This workinggroup should also engage with relevant international bod-ies and ensure that the international structure can encom-pass their dissemination work. The working group mustalso consider how the international structure will developthe scientific authority needed to deliver on the tasks be-low.Once formed, the international structure should1. survey existing good practice in different countriesand in international organizations, and encouragethe exchange of ideas2. establish a procedure for validation of information,including a method for embodying that validationwithin the information, for example by a certificationmark;3. identify, validate and provide links to existing goodinformation that can assist education and awareness-raising amongst all types of stakeholders in spaceweather;4. identify gaps in this information, promote efforts tofill those gaps and provide links to validated outputs;5. encourage adaptation of information to best suit theneeds of particular groups and countries, includingtranslation into local language and adaptation to lo-cal culture; and6. compile information on sources of space weather re-search data and of space weather applications andservices, and provide links to these sources.To support the worldwide dissemination of space weatherknowledge the international structure should establish aninternet-based system that can point to a range of vali-dated information on space weather covering the differentneeds of all types of stakeholders. Given the rapid evolu-tion of internet technologies, we do not seek to prescribehow the system be implemented, rather we recommendthat the international structure, once established, reviewthe options available, having regard to the need for a re-silient and sustainable system, and for ease of use by con-tributors and users around the world.Consideration should be given on whether the interna-tional structure should seek to validate space weather ser-vices and data access. However, it may be best to avoidthis as it may open up significant legal issues, especiallyin respect of commercial services.27 . Execute an international, inter-agency assessmentof the state of the field to evolve priorities subject to sci-entific, technological, and user-base developments to guideinternational coordination:
With rapidly changing technologies and advancing un-derstanding the focus priorities of the science of spaceweather are likely to evolve over time, so that a periodicevaluation of the state of the field will prove useful to pro-vide guidance to the research organizations. Such roadmapstudies should identify options for agencies to align domes-tic and international priorities, to identify projects mostsuitable for direct collaboration, and to identify where in-ternational activities might make domestic investments toaddress scientific priorities less urgent or superfluous.
Recommendation:
We recommend that a roadmapfor the science of space weather be conducted at a 5-yearcadence, ideally timed to provide information to nationalstrategic assessments such as the Decadal Surveys in theUS or to such multinational funding programs like EUH2020 program and its successors. These should be in-ternational projects, led by representatives from the sci-entific community, and involving at least representativesof all major space agencies as well as research organiza-tions working on the ground segments of space weather.Moreover, agencies should regularly appoint inter-agencyscience definition study teams with representatives fromagencies, the science community, and the space-weatheruser community to find optimal balance between scientificpotential of new missions by themselves and as part of theSun-Earth System observatory, where the potential valueas element of the system observatory should weigh heavilyin its design and evaluation.
D. Develop settings to transition research tools to op-erations.
With the rapid advance of scientific knowledge andthe continuous evolution of operational needs, it is essen-tial that a constant cycle of improvement occur in spaceweather forecasting/specification capabilities. This cycleinvolves the development and utilization of new capabili-ties that improve services, and it involves the continuousfeedback of the highest priority operational needs. Re-search tools comprise scientific models and research (mea-surement) infrastructure. The latter may require invest-ment in order to be considered operational with respect todata availability, timeliness, quality and reliability. Oper-ational tools need to be consistent in order to comply withany given Service Level Agreement and to be consideredeffectively operational. Recommendation: We recommendthat a roadmap for research-to-operations (R2O) transi-tion be conducted at a 5-year cadence, timed to provideinformation to, and take information from, a parallel sci-ence roadmap. This R2O roadmap should focus on spe-cific, high priority activities that can achieve measurableprogress on service metrics.In order for research models to be considered suitablefor use in a forecast center, they should be confronted to a set of standardized evaluation criteria, such as: accuracy ofoutput; confidence level and uncertainty estimation; sta-bility; maintainability and scalability; support and doc-umentation; autonomy and ease of use (forecasters andoperators may not be specialists).
Recommendation:
We recommend that the inter-national community establish standardized practices andprocedures to evaluate research models, similar to the GEM/-SHINE/CEDAR challenges. Internationally agreed met-rics for model and forecast performance evaluation shouldbe established.It is vital to implement and support reliable archivingof data collections and to guarantee streamlined access toarchives. Efficient dissemination of archived and near realtime data is a prerequisite for maintaining reliable serviceoperation.
Recommendation:
We recommend that a commonset of space weather metadata be developed in order tofacilitate harvesting and interpreting data. In addition,the development of standardized interfaces to data repos-itories is strongly encouraged, as well as common dataanalysis toolkits (standardized software packages). Thisshould build on existing international programs that haveaddressed the provision of standard metadata for the Sun-Earth domain, including the NASA-led SPASE project,the ESPAS and HELIO projects in the EU FP7 programme,ESA’s Cluster Active Archive, and the IUGONET projectin Japan.
E. Partner with the weather and solid-Earth communi-ties to share infrastructure and lessons learned:
The uppermost troposphere and the thermosphere/meso-sphere above it influence ionospheric processes. More-over, space weather phenomena may couple into long-termregional weather and climate, as has been proposed forcosmic-rays modulation and solar spectral irradiance vari-ations.Partnering with climate/weather stakeholders is ben-eficial also on another front: space weather scientists areonly beginning to learn how to assimilate observations intodata-driven ensemble models, and can learn much fromthe meteorological community. Space weather forecastinglooks to the example of terrestrial weather forecasting as afield with similar goals and much longer history and expe-rience. In particular, many of the advances in terrestrialweather forecasting have come about by the augmentationof physics-based models with advanced statistical meth-ods, such as data assimilation and ensemble modeling. Theadvancement of space weather forecasting likely requiressimilar endeavors. However, we must recognize that forsome regimes (such as in Earth’s ionosphere) the meteo-rological techniques can be borrowed with little modifica-tion, while in other regimes (particularly where the datais sparse) new techniques will need to be developed.Yet another reason for partnerships with weather andsolid-Earth sciences could be the sharing of stations forgeomagnetic, magnetotelluric, and ionospheric measure-28ents in the much-needed expanded web of ground-basedmeasurement locales.Engagement with the solid-Earth geophysics commu-nity is vital for space weather studies of GIC, since thegeomagnetic induction of electric field inside the Earth isa critical element in the causal chain of physics leading toadverse GIC impacts on technological systems. The solid-Earth geophysics community has excellent expertise in thisarea, since geomagnetic induction is also a key techniquefor exploring the sub-surface structure of the Earth downto depths of at least several hundred kilometers. Thustheir engagement in space weather studies is vital.
Recommendation:
We recommend intensification andformalization of coordination between the ITM and cli-mate/weather research and modeling communities, specif-ically (a) to develop, in the mid-term, whole atmospheremodels (i.e. coupled models ranging from the troposphereinto the high ITM domain), (b) to learn about data assim-ilation, ensemble modeling and other advanced statisticaltechniques in forecasting scenarios, (c) to partner in themulti-use of ground stations for both terrestrial and spaceweather, and (d) to analyze possible pathways by whichspace weather could impact Earth global or regional cli-mate. In the US, NSF/UCAR is the natural focal point forthis research, coordinated with NASA/SMD Heliophysicsresearch in ITM physics, while organizations like WMOor IUGG may be engaged as an enabling coordinator andas an existing multi-national organization for intergovern-mental communication. We also recommend strengthen-ing ties to the solid-Earth community to support transfor-mation of geomagnetic variability to electric fields involvedin GICs.
6. Research: observational, numerical, and theo-retical recommendations
The highest-priority scientific needs that were only verybriefly mentioned in Section 5.1 are presented in more de-tail in this section, and complemented by specific instru-mentation and model concepts in Section 7. In this Sec-tion, we identify the needs (a) to maintain existing obser-vational capabilities, (b) to develop modeling capabilities,enable archival research, or improve the data infrastruc-ture, and (c) to construct new space-based and ground-based instrumentation. By their nature, these three classesof investments can be implemented (a) immediately, (b) ona time scale of a year or two, or (c) on a time scale of about4 to 10 years.The recommendations formulated in this section aretaken from the impact tracings (discussed in AppendixB) that were initially produced looking separately at thesolar-heliospheric domain and at the geospace domain (assummarized in Appendices D and E, respectively). In thissection we merge all those requirements, sorting them intothree general clusters of recommendations that we shallrefer to as pathways of research. Pathway I collects theneeds for the full Sun-Earth domain that are related to the need to obtain forecasts more than 12 hrs ahead of themagnetic structure of incoming CMEs to improve alertsfor GICs and related ionospheric variability. Pathway IIwill need at least part of the new knowledge developedwithin Pathway I to forecast the particle environments of(aero-)space assets and to improve environmental speci-fication and near-real time conditions. Pathway III is aparticularly challenging one, aiming to enable pre-eventforecasts of solar flares and CMEs, and related solar X-ray, EUV and energetic particle storms for the near-Earthsatellites, astronauts, ionospheric conditions, and polar-route aviation, including all-clear conditions. From theviewpoint of solar physics, Pathway I contains those re-quirements that are most feasible to do within next fiveyears. From the viewpoint of geospace research PathwayI contains the requirements linked with the advancementsto be achieved from solar physics and support especiallyGIC/GMD. With the requirements of Pathway I fulfilled,we should be able to improve GIC/GMD forecast in allconditions. Also in GNSS and aero-space domains signifi-cant improvement will be achieved, but the issues involvedwill not be fully solved in Pathway I.From the viewpoint of solar physics, Pathway I con-tains much the same things as Pathway II. The geospacerequirements are mostly separate in Pathway II becausethey address largely complementary physics in geospace,while they will gain significant benefit from the solar andheliospheric work on the variable solar wind supported byPathway I. Aero-space assets are here the main impactarea, but the models discussed in Pathway II will sup-port the efforts to understand D-layer absorption (causedby RB energetic particle precipitation) and thus they willhelp also with HF communication.Recommendations in Pathway III are from the view-point of solar physics much more challenging than thoseof Pathways I and II because they concern forecasts beforeany substantial event has occurred on the Sun.
Pathway I:.
To obtain forecasts more than 12 hrs aheadof the magnetic structure of incoming coronal mass ejec-tions to improve alerts for geomagnetic disturbances andstrong GICs, related ionospheric variability, and geospaceenergetic particles:Maintain existing essential capabilities: • magnetic maps (GBO, SDO), X/EUV images at arc-sec and few-second res. (SDO; Hinode), and solarspectral irradiance observations; • solar coronagraphy, best from multiple perspectives(Earth’s view and L1: GBO and SoHO; and well offSun-Earth line: STEREO); • in-situ measurements of solar wind and embeddedmagnetic field at, or upstream of, Sun-Earth L1 (ACE,SoHO; DSCOVR); • for a few years, measure the interaction across thebowshock/magnetopause (as now with Cluster/ART-29MIS/THEMIS; soon with MMS), to better under-stand wind-magnetosphere coupling; • satellite measurements of magnetospheric magneticand electric fields, plasma parameters, soft auroraland trapped energetic particle flu variations (e.g.,Van Allen Probes, LANL satellites, GOES, ELEC-TRO-L, POES, DMSP); • ground-based sensors to complement satellite datafor Sun, heliosphere, magnetosphere, and iono-/thermo-/mesosphere data to complement satellite data.Archival research, develop data infrastructure, or modelingcapabilities: • near-real time, observation-driven 3D solar active-region models of the magnetic field to assess desta-bilization and estimate energies; • data-driven models for the global solar surface-coronalfield; • data-driven ensemble models of the solar wind in-cluding magnetic field; • data assimilation techniques for the global ionosphere-magnetosphere system for nowcasts and near-termforecasts to optimally use and to coordinate groundand space based observations to meet user needs.Compare models and observations, ideally in selectlocations where laboratory-like test beds exist or canbe developed at a few informative latitudes. • coordinated system-level research into large-scale rapidmorphological changes in the Earth’s magnetotailand embedded energetic particle populations (usingdata from, among others, SuperDARN, SuperMAG,AMPERE, etc.); • system-level study of the mechanisms of the particletransport, acceleration, and losses driving currentsand pressure profiles in the inner magnetosphere; • stimulate research to improve global geospace model-ing beyond the MHD approximation (kinetic, hybrid,. . . ) • develop the ability to use chromospheric and coronalpolarimetry to guide full-Sun corona-to-heliospherefield models.Deployment of new/additional instrumentation: • binocular imaging of the solar corona at ∼ ∼ ◦ -20 ◦ sepa-ration between perspectives; • observe the solar vector field at and near the surfaceand the overlying corona at < • (define criteria for) expanded in-situ coverage of theauroral particle acceleration region and the dipole-tail field transition region (building on MMS) to de-termine the magnetospheric state in current (THEMIS,Cluster) and future high-apogee constellations, usinghosted payloads and cubesats where appropriate; • (define needs, then) increase ground- and space-basedinstrumentation to complement satellite data of mag-netospheric and ionospheric variability to cover ob-servations gaps (e.g., in latitude coverage or overoceans); • an observatory to expand solar-surface magnetogra-phy to all latitudes and off the Sun-Earth line [forwhich the Solar Orbiter provides valuable initial ex-perimental views]; • large ground-based solar telescopes (incl. DKIST)to perform multi-wavelength spectro-polarimetry toprobe magnetized structures at a range of heights inthe solar atmosphere, and from sub-active-region toglobal-corona spatial scales; • optical monitors to measure global particle precipi-tation [such as POLAR and IMAGE] to be used indata assimilation models for GMD and ionosphericvariability. Pathway II:.
For the particle environments of (aero)spaceassets, to improve environmental specification and near-real-time conditions. In addition to the remote-sensingand modeling requirements for Pathway 1:Maintain existing essential capabilities: • develop particle-environment nowcasts for LEO toGEO based on observations of electron and ion pop-ulations (hard/ ∼ MeV and soft/ ∼ keV; e.g., GOES,. . . , striving for intercalibrated data sets with betterbackground rejection, for at least a solar cycle), andof the magnetospheric field [see GMD/GIC recs.]; • maintain a complement of spacecraft with high res-olution particle and field measurements and definedinter-spacecraft separations (e.g., the Van Allen Probes).Archival research, develop data infrastructure, or modelingcapabilities: • specify the frequency distributions for fluences of en-ergetic particle populations [SEP, RB, GCR] for thespecific environment under consideration, and main-tain access to past conditions; • develop, and experiment with, assimilative integratedmodels for RB particle populations towards forecastdevelopment including ionosphere, thermosphere andmagnetosphere, including the coupling from lower-atmospheric domains, and validate these based onarchival information.30eployment of new/additional instrumentation: • increased deployment of high- and low-energy par-ticle and electromagnetic field instruments to en-sure dense spatial coverage from LEO to GEO andlong term coverage of environment variability (in-cluding JAXA’s ERG [Exploration and energizationof Radiation in Geospace; launch in 2015]. Com-bine science-quality and monitoring instruments for(cross) calibrations, resolution of angular distribu-tions, and coverage of energy range. Pathway III:.
To enable pre-event forecasts of flares andsolar energetic particle storms for near-Earth satellites, as-tronauts, ionospheric conditions, and polar-route aviation,including all-clear conditions. In addition to the remote-sensing and modeling requirements for Pathway I:Maintain existing essential capabilities: • solar X-ray observations (GOES); • observe the inner heliosphere at radio wavelengths tostudy shocks and electron beams in the corona andinner heliosphere; • maintain for some years multi-point in-situ observa-tions of SEPs off Sun-Earth line throughout the innerheliosphere (e.g., L1, STEREO; including ground-based neutron monitors). • maintain measurements of heavy ion composition (L1:ACE; STEREO; near-future: GOES-R).Archival research, develop data infrastructure, or modelingcapabilities: • develop data-driven predictive modeling capabilityfor field eruptions from the Sun through the innerheliosphere; • investigation of observed energetic particle energiza-tion and propagation within the inner-heliosphericfield, aiming to develop at least probabilistic fore-casting of SEP properties [see also Pathway-1 recom-mendations for heliospheric data-driven modeling]; • new capabilities for ensemble modeling of active re-gions subject to perturbations, to understand fieldinstabilities and energy conversions, including bulkkinetic motion, SSI, and energetic particles.Deployment of new/additional instrumentation: • new multi-point in-situ observations of SEPs off Sun-Earth line throughout the inner heliosphere to im-prove models of the heliospheric field and understandpopulation evolutions en route to Earth (e.g., SolarOrbiter, Solar Probe Plus).
7. Concepts for highest-priority research and in-strumentation
In this section we present brief summaries of the ra-tionales for the (new or additional) research projects andinstrumentation investments given the highest priorities inthe preceding section. These summaries, expanded uponin In 6, are meant to illustrate possible investments thataddress the identified scientific needs towards an integratedapproach to the space-weather science. These investmentconcepts demonstrate possible approaches that we deemfeasible in terms of technological requirements and bud-getary envelopes, but we emphasize that science definitionteams focusing on the top-level scientific needs may wellbe able to identify and shape other options.
We identified a very high-priority requirement to char-acterize the solar-wind magnetic field, and in particularthe field involved in CMEs. To address that, in-situ mea-surements upstream of Earth at the Sun-Earth L1 sentinelpoint are insufficient. Moreover, technological means andbudgetary resources are inadequate to position in situ sen-tinels on the Sun-Earth line sufficiently close to the Sun,or to launch a fleet of moving sentinels with always onenear to that position. The variable solar-wind magneticfield associated with active-region eruptions must conse-quently be obtained from forward modeling of observedsolar eruptions through the embedding corona and innerheliosphere, based on the inferred magnetic field of erupt-ing structures. A key science goal in this roadmap is con-sequently the determination of the origins of the Sun’s im-pulsive, eruptive activity that will eventually drive magne-tospheric and ionospheric variability. Deriving that fromsurface (vector-) field measurements only has been shownto yield ambiguous results at best.One way to constrain the 3D active-region field makesuse of novel modeling methods that can utilize the coro-nal loop geometry to constrain the model field, most suc-cessfully when 3D information on the corona is available.As described in Appendix F.1, binocular imaging of theactive-region corona at moderate spatio-temporal resolu-tion enables the 3D mapping of the solar active-regionfield structure prior to, and subsequent to, CMEs, therebyproviding information on the erupted flux-rope structure.This could be achieved by a single spacecraft some 10 to20 degrees off the Sun-Earth line if combined with, e.g.,the existing SDO/AIA or other appropriate EUV imagers,or - if these are no longer available - by two identicallyequipped spacecraft off the Sun-Earth line with approxi-mately 10-20 heliocentric degrees of separation.A second new observational capability is also priori-tized in this context to derive information on low-lyingtwisted field configurations in the deep interiors of unsta-ble active regions before and after eruptions is key to de-termining what propagates towards Earth to drive space31eather. The magnetic stresses in these regions that areinvolved in CMEs cannot be observed directly, but requiremodeling based on observations of the vector magneticfield at and immediately above the solar surface (in thesolar chromosphere), guided by higher structures that areobserved within the overlying atmosphere (differentiatedby temperature from the low, cool, dense chromosphereto the high, hot, tenuous, field-dominated corona). Withthe help of these atmospheric structures that outline themagnetic field and the parallel electrical currents we candetermine the fraction of the system’s free energy thatis converted to power eruptions. Binocular imaging isunlikely to succeed for very low-lying, compact magneticstructures within active regions. Moreover, chromosphericvector-magnetic measurements in addition to photosphericones are expected to aid in the mapping of the 3D activeregion field as this provides observational access to elec-trical currents threading the solar surface, and observingthe details of the low-lying flux ropes before, during, andafter eruptions to quantify the 3D field ejected into theheliosphere.The information on the low-lying magnetic field and theelectrical currents within can be obtained by a space mis-sion (outlined in Appendix F.2) that obtains vector-mag-netic measurements of active regions at the solar surfaceand within the overlying chromosphere, combined withoptical and EUV imaging of the solar atmosphere from10,000K up to at least 3MK, all at matching resolutions oforder 0.2 arcseconds, to map all field structures that maycarry substantial electrical currents.
Like explained in Section 4, some key processes in thechain of magnetospheric energy release leading to largefield-aligned currents and hence GICs remain poorly known: • the dynamics nearer to Earth at the inner edge ofthe plasma sheet where bursty bulk flows brake andpresumably give rise to a number of more or lesseffective plasma instabilities, • and the coupling of these processes into the iono-sphere along magnetic field lines.In particular, the processes that control the rate of en-ergy transport and the partition between competing routesof dissipation in the coupled (M-I) system remain insuffi-ciently understood. We do not know the conditions whichcontrol the partitioning and exchange of energy betweencurrents, waves, and particles that are believed to act asa gate for the ability of the tail to drive FACs through toclosure in the ionosphereTo uncover the processes in this interface domain, atwo-constellation satellite mission architecture is proposed(detailed in Appendix F.3), where the challenge lies not inadvanced instrumentation but in the positioning of a suf-ficient number of spacecraft at the two key locations in space. The first constellation should focus on plasma in-stabilities and flow braking at the inner edge of the plasmasheet, in the transition region from dipolar to tail-like mag-netic fields. It would probe the three-dimensional plasmaand electrodynamic fields (E and B) in the transition re-gion, from close to geosynchronous orbit to around 10-12 R E during the course of the mission. This constellationcould consist of a central mother spacecraft accompaniedby some 4 smaller spacecraft approximately 1 R E from themother, providing coverage in the azimuthal and radialdirections.The second, coordinated constellation is to focus on the(M-I) coupling in the auroral acceleration region on conju-gate auroral field lines below. It would provide multi-pointplasma and electrodynamic fields in the auroral accelera-tion region to determine the dynamical M-I coupling, ataltitudes of around 4000 km to 1 Re, in a configuration de-signed to resolve spatio-temporal ambiguity of the filamen-tary FACs and to distinguish between alternative particleacceleration processes.These constellations should be supported by conjugateauroral imaging from the ground, and if possible also fromspace, to probe both global and small scale ( <
100 km)structures. LEO satellites to additionally monitor the pre-cipitating electrons as a measure of conductivity changesbelow will provide valuable complementary measurements.On the other end of the coupled system of the magne-tosphere measurements of incoming flows in the centralplasma sheet from the more distant tail are required toassess incoming flow characteristics in the same meridian.These could be provided by existing assets, such as Geo-tail, Cluster, THEMIS, or perhaps by MMS in an extendedmission phase. An upstream solar-wind monitor is, as al-ways, required as well. The success of the constellationsproposed here, as is true for the overall geospace observingsystem, is crucially dependent of measurements from richnetworks of ground-based instruments, including (a) mag-netometers to observe how electric currents in the iono-sphere are modified by space weather, plus (b) a wide va-riety of radar and radio techniques to monitor changes inthe density, motion and temperatures of ionospheric plas-mas, as well as (c) optical techniques to measure thermo-spheric winds and temperatures. These data sources areall key inputs to aid the identification of the onset loca-tion and the resolution of the spatio-temporal ambiguity ofthe processes leading to large dB/dt. Ground-based datasupport also the development of improved models of theatmosphere and its response to space weather, increasinglyso as we advance assimilative approaches. As outlined inAppendix F.4, we need to promote these ground-based net-works as a global system for scientific progress on spaceweather, so that each instrument provider (and funder)sees how their contribution fits into the wider picture, i.e.that a local contribution builds and sustains local accessto a global system.32 .3. Global coronal field to drive models for the magnetizedsolar wind
The Sun’s surface magnetic field is a vital ingredientto any predictive model of the global magnetic field thatdefines the structure of the heliosphere, including the po-sition of the heliospheric current sheet and the regions offast and slow solar wind, and plays a key role in spaceweather at Earth: (1) the interaction of CMEs with theambient field impacts their geo-effectiveness; (2) the con-nection of the heliospheric magnetic field to CME-relatedshocks and impulsive solar flares determines where solarenergetic particles propagate, and (3) the partitioning ofthe solar wind into fast and slow streams is responsiblefor recurrent geomagnetic activity. In order to obtain themagnetic-field information that is needed to forecast thefield arriving at Earth over a day in advance, the interac-tion of that field evolving from near the solar surface intothe field moving through the corona-heliosphere boundarymust be known.Models for the global solar magnetic field typically usemagnetic maps of the photospheric magnetic field builtup over a solar rotation, available from ground-based andspace-based solar observatories. Two well-known problemsarise from the use of these “synoptic” maps. First, suchmaps are based on solar conditions that lie as much as27 days in the past of an always-evolving surface field.Second, the field in the Sun’s polar regions is poorly ob-served, and consequently the high-latitude fields in thesemaps are filled with a variety of interpolation and extrap-olation techniques. These two observational problems canstrongly influence the global magnetic field model: poorlyobserved active regions near the limb (as viewed fromEarth), unobserved regions beyond the limb, and inaccu-rate polar field estimates can introduce unacceptable er-rors in the high-coronal field on the Earth-facing side ofthe Sun.To address these observational problems, we need toobtain photospheric magnetograms off of the Sun-Earthline, particularly of the east limb (just prior to becomingvisible again on the Earth-facing side of the Sun that isthe portion of the solar field with the oldest observationsas viewed from Earth), to complement magnetograms ob-tained along the Sun-Earth line by SDO and ground-basedobservatories; Appendix F.5 describes a mission trailingEarth its orbit to provide the needed observations. More-over, we need to obtain magnetograms of the Sun’s polarfields over a few years to understand the evolution of theSun’s polar magnetic flux. As described in Appendix F.5,the Solar Orbiter will provide some of the initial measure-ments needed by providing at least a good calibration ofthe highest-latitude solar field; but the orbit of the SolarOrbiter is such that magnetogram information of the so-lar far side as viewed from Earth will be provided only onoccasion with long gaps between relatively short observ-ing intervals and with long delays before the observationscan be telemetered to Earth: magnetic field coverage at a cadence fast enough to follow active region evolution fullyaround the Sun is not possible with the Orbiter.The improved magnetographic coverage of the solarsurface is needed to improve the models for the corona-heliospheric interface and to feed heliospheric magneto-hydrodynamic models: to yield meaningful predictions ofCME magnetic structure, it is necessary to utilize an accu-rate representation of the time-evolving global solar coro-nal magnetic field as input to models of prediction, erup-tion and propagation of CMEs through the solar wind.Such models ultimately will need validation by samplingtheir results near Earth, but before that they need guid-ance as to the physical approximations made in the solarcoronal field and plasma model. Such guidance comes fromcoronagraphic polarimetric observations, which we shallneed to learn to absorb into global coronal-heliosphericmodels.New observations and modeling techniques are needed(as summarized in Appendix F.6): we propose to startwith simulated multi-wavelength coronal magnetometricobservables for constraining the global magnetic field, tobe incorporated into global MHD models. In order to reachthis goal, we propose model testbeds (c.f., Section 5.2, Rec-ommendation II) for synthetic polarimetric measurementsrelated to the Zeeman and Hanle effects, gyroresonanceand gyrosynchrotron radiation, thermal (free-free) emis-sion, and coronal seismology. These simulated observablescan be tested as drivers for, and ultimately assimilationinto, global MHD coronal models. Guided by the outcomeof these experiments, observations need to be obtained,most likely requiring new instrumentation (see AppendixF.6).The MHD models for the global corona are the naturalfoundation for plasma and field models for the overall he-liosphere. The latter are already being worked on, specif-ically for the background quiescent solar wind structure,but they are not yet driven by the full magnetic input fromactual solar conditions simply because that information isyet to be derived as described above. Once that informa-tion is available, fully dynamic models for the entire innerheliosphere need to be strongly supported.
The response of magnetosphere to solar wind drivingdepends on the previous state of magnetosphere. Sim-ilar sequences in energy, momentum and mass transferfrom the solar wind to magnetosphere can lead in somecases to events of sudden explosive energy release whilein other cases the dissipation takes place as a slow semi-steady process. Comprehensive understanding on the fac-tors that control the appearance of the different dissipa-tion modes is still lacking, but obviously global monitor-ing of the magnetospheric state and system level approachin the data analysis would be essential to solve this puz-zle. Continuous space-based imaging of the auroral ovalwould contribute to this kind of research in several ways.33he size of polar cap gives valuable information about theamount of energy stored in the magnetic field of magneto-tail lobes. Comparison of the brightness of oval at differentUV wavelengths yields an estimate about the energy fluxand average energy of the particles that precipitate frommagnetosphere to ionosphere. These estimates are not asaccurate as those from particle instruments on board LEOsatellites, but the additional value comes from the capabil-ity to observe all sectors of the oval simultaneously. Suchview is useful especially in the cases where the magneto-sphere is prone to several subsequent activations in thesolar wind. The shape and size of the oval and intensityvariations in its different sectors enable simultaneous mon-itoring of magnetosphere’s recovery from previous activitywhile new energy comes into the system from a new eventof dayside reconnection.There is consequently a need to achieve continuouslyglobal UV or X-ray images to follow the morphology anddynamics of the auroral oval, at least in the Northern hemi-sphere, but occasionally also in the southern hemisphere.Imager data combined with ground-based networks simi-larly as suggested above in Section 7b allows solving theionospheric Ohm’s law globally which yields a picture ofelectric field, auroral currents and conductances with goodaccuracy and spatial resolution. This would mean a leapforward in our attempts to understand M-I coupling, par-ticularly the ways how ionospheric conditions control thelinkage, e.g., by field-aligned currents (see Appendix F.7for more discussion).
Trapped energetic particles in the inner magnetosphereform radiation belts. Solar wind variability modifies trappedparticle transport, acceleration, and loss. The inner pro-ton belt is relatively stable, but the outer radiation beltcomprises a highly variable population of relativistic elec-trons. Relativistic electrons enhancements are an impor-tant space weather factor with a strong influence on satel-lite electronics. Around half of magnetic storms are fol-lowed by an enhancement of relativistic electron fluxes.It appears that the pre-existing magnetospheric state is acritical factor in radiation belt variability; for example, ef-ficient production mechanisms appear to need a seed pop-ulation of medium-energy electrons. Storm-time magne-tospheric convection intensification, local particle acceler-ation due to substorm activity, and resonant wave-particleinteraction are the main fundamental processes that causeparticle energization and loss.Current understanding of energetic electron and pro-ton acceleration mechanisms within the radiation belts isinsufficient to discriminate between the effectiveness of dif-ferent energization, transport, and loss processes at differ-ent L-shells and local times. Quantitative assessment ofthe predictive properties of current and emerging models isthus essential. Given the current very limited understand-ing of geo-effectiveness, excellent monitoring of the realtime environment (nowcasting) is the most useful product that can be provided to satellite operators. This, and well-characterized descriptions of historical events, can be usedto interpret failures and improve the resilience of space-craft design. We propose intensified support for compre-hensive modeling of the behavior of particles within theradiation belts based on multi-point in-situ observations(see Appendix F.8 for more details).
SEPs present a major hazard to space-based assets.Their production is associated with large flares and fastCMEs in the low corona, typically originating from com-plex active regions. The prompt response can arrive atEarth in less than an hour from the onset of eruption,and some times in a few minutes after the onset of theflare in the case of a well-connected, relativistic particleevent. This is often followed by continued high SEP fluxesas a CME shock propagates out from the Sun and mayexhibit a distinct peak, rising by as much as two ordersof magnitude, as the CME shock passes over the point ofmeasurement. The particles in this peak are often referredto as Energetic Storm Particles (ESPs) and are particlestrapped close to the shock by plasma turbulence associ-ated with the shock (e.g., Krauss-Varban, 2010). Theymay provide most of the particle fluence within a gradualSEP event. While warning of events in progress is cer-tainly important, many users require significantly longerwarning, e.g., 24 hours (e.g., all-clear periods for Extra-Vehicular Activities for astronauts). Recent multi-pointobservations of SEP events off the Sun-Earth line showthat prompt energetic particles have access to a wide lon-gitudinal extent for some events. They also show that fora large proportion of SEP events, the prompt energeticparticles do not propagate along the normal Parker spi-ral but in the magnetic field of a pre-existing CME. ESPscan also reach energies in excess of 500 MeV and also posemajor space weather hazard. The ESPs represents a “de-layed” radiation hazard traveling with the CME shock, sothat there is a good chance of making accurate predictionsof the onset times of ESP events. Thus the key researchchallenge is how the intensity, duration, and arrival timeof the prompt response depends on the SEP event nearthe Sun, presence of a type II or IV radio burst in thenear-Sun interplanetary medium, and the source locationof the flare/CME that drives the shock.In order to further the understanding of these SEP pop-ulations, we recommend that in addition to the recommen-dations for the solar and heliospheric domains above, thereshould be multi-point in-situ observations of SEPs off theSun-Earth line and possibly closer to the Sun than theL1 distance. For this we recommend extensive use of anyplanetary and inner-heliospheric missions that may occurin the future (see Appendix F.9 for more details).34 . In conclusion
Throughout the development of this roadmap, we wereas much impressed by the observational coverage of theSun-Earth system that is currently available as by thesparseness of that coverage given the size, complexity, anddiversity of conditions of the system. Our main recommen-dations are readily condensed into a few simple phrasesthat reflect the team’s philosophy: make good use of whatwe have now; bring considerable new resources to bear onthose problem areas that have the largest leverage through-out the overall system science; and be efficient with thelimited budgets that are available in the near future. Outof this philosophy come the recommendations that stressthe paramount importance of system modeling using thesystem observatory, of collaboration and coordination oninstrumentation and data systems, and of a shift from afew expensive, comprehensive satellite missions to invest-ments in many efficient small satellites that target specificcapability gaps in our current fleet.The desire expressed in the charge to the team fordemonstrable improvements in the provision of space weatherinformation will need to be evaluated after our recommen-dations have started to be implemented. Our recommen-dations are formulated clearly with an expectation to meetthat desire: knowing how to model the field in solar erup-tions before its arrival at Earth, better understanding ofthe triggers and inhibitors of instabilities in the magneto-spheric field, improved tracing of the sources and sinks ofenergetic particle populations from Sun to radiation belts,and greater modeling capabilities of the drivers of iono-spheric variability, to name a few of the targets of thisroadmap, appear all within reach if targeted investmentsare made.One key challenge overall is the transformation into aneffectively functioning global research community. Manyof our recommendations are meant as catalysts to this pro-cess: open data, shared investments, code developmentas community effort, and coordinated instrumentation de-ployment are all part of this.In order to stimulate implementation of our recommen-dations as well as to assess their impact we recommendthat the research community keep a finger on the pulseas active players and as stewards of the investments: thisroadmap needs updates and course changes by the researchcommunity and their funding agencies every few years toremain relevant.
Appendix A. Roadmap team and process
The roadmap team was appointed by the COSPARleadership taking advice from the COSPAR Panel on SpaceWeather and the steering committee of the InternationalLiving With a Star (ILWS) program. The team orga-nized its work to ultimately summarize its findings in threekey areas: (1) observational, computational, and theo-retical capabilities and needs; (2) coordinated collabora- tive research environment, and (3) collaboration betweenagencies and between research and customer communi-ties. The team’s deliberations proceeded hierarchically:a) key research questions to be addressed to make demon-strable advances in understanding the space environmentand the space weather services derived from that; b) re-search methodologies required to effectively address thoseresearch questions, and c) specific crucial observables, mod-els, data infrastructures, and collaborative environmentsthat enable those research methodologies. Specific rec-ommendations for observational, modeling, and data in-frastructures are grouped into three pathways. The path-ways reflect the assessed scientific urgency, the feasibilityof implementations, and the likelihood of near-term suc-cess. Subsequent pathways need the recommendations ofpreceding ones implemented at least to some extent toachieve full success, but can be initiated in parallel. Theroadmap team does not mean to imply priorities in thesense of scientific or societal importance in these path-ways, but developed them to devise a pragmatic, feasible,affordable, international implementation plan to meet theroadmap’s charge.The roadmap team met for three face-to-face work-ing meetings: twice in Paris at COSPAR headquarters(November 2013 and September 2014) and once in Boul-der (April 2014, in conjunction with the US Space WeatherWeek). In between these work was coordinated in teleconsevery second week and email exchanges. Input from thecommunity was sought through presentations at variousmeetings, notifications of an email input channel throughcommunity newsletters, and by personal discussions withthe team membership. An initial draft of the Roadmapwas presented in an interdisciplinary lecture at the CO-SPAR general assembly in Moscow in August 2014, fol-lowed by a dedicated community discussion session. Priorto the completion of the full written report, the princi-pal findings were summarized in an Executive Summary(packaged as a brochure) and made available for final com-ments on the COSPAR web site , and handed out at theUS LWS meeting and the European Space Weather Week,both in November 2014.The roadmap team was supported in its activities byan oversight group from agencies and research organiza-tions: Philippe Escoubet (ESA, ILWS Steering CommitteeChair, ESA), Madhulika Guhathakurta (NASA, ILWS),Jerome Lafeuille (WMO, ICTSW, ILWS), Juha-Pekka Lun-tama (ESA-SSA Applications Programme, ESA), AnatoliPetrukovich (RFSA, ILWS vice-chair), Ronald Van derLinden (International Space Environment Service), andWu Ji (Chinese National Space Science Centre, COSPARDeputy Chair).For a partial compilation of space weather resources,we refer the reader to web sites such as at WMO/OS- https://cosparhq.cnes.fr/sites/default/files/executivesummary -compressed.pdf igure A.4: Logical structure of the roadmap: After tracing impactpathways, requirements are prioritized in three major aspects of theresearch infrastructure, after which opportunities and challenges areidentified in each to reach a set of prioritized recommendations. CAR (Observing Systems Capability Analysis and Re-view Tool), the WMO Space Weather Portal , and theonline Space Weather Catalogue . Appendix B. Roadmap methodology: tracing sam-ple impact chains
The complexity of the interconnected system of phys-ical processes involved in space weather precludes a sin-gle, comprehensive, yet understandable and concise explo-ration of the network as a whole. To effectively and ef-ficiently address its charge the roadmap team thereforedeveloped a strategy that focuses on three largely dis-tinct space weather phenomena with largely complemen-tary impact pathways on societal technologies: A) electri-cal systems via geomagnetic disturbances, B) navigationand communication impacts from ionospheric variability,and C) (aero-)space assets and human health via ener-getic particles. These impact pathways collectively probethe physics of the Sun-Earth system whose variability isquantified, for example, in the G (geomagnetic), R (radioblackout), and S (radiation) storm scales used by NOAA’sSpace Weather Prediction Center. The physical processesinvolved in the probed pathways often map across thesestorm scales that are but one way to quantify some of theattributes of space weather. No three pathways or scalescan characterize the rich spectrum of space weather phe-nomena, just as terrestrial weather forecasts typically donot characterize the multitude of phenomena of weather,but in both cases a carefully selected set will encompassmuch of the dynamics and will help users understand thethreat of space and terrestrial weather in the coming hoursand days. Subsequent to this impact tracing, the roadmap teamintegrated these parallel assessments into a comprehensiveview with associated requirements and prioritized actionsto be taken to advance our understanding of space weatherand to improve the quality of space weather services. Wedo so by looking from the Sun, through the heliosphere,into geospace which we use to describe the domain encom-passing the coupling region between solar wind and thegeomagnetic field, throughout the geotail, and down intothe high layers of Earth’s atmosphere. A summary of theorganizational structure is shown in Fig. A.4.
Appendix C. State of the art in the science ofspace weather
Appendix C.1. Achievements
The research activities in “space weather” are increas-ing rapidly: for example, based on entries in the NASAAstrophysics Data System, over a recent 15-year period(1997-2012) the number of publications per year has in-creased by a factor of 12 (refereed publications) to 16(all publications) to 925 publications per year in total onthe topic for 2012. This rapid growth in interest in, andimplied support for, space weather research (see Fig. 1)has advanced our insights in and understanding of spaceweather tremendously. That advance largely coincidedwith the growth of space-based observational capabilities,whose discoveries included the direct confirmation of theexistence of the solar wind in the early 1960s (with undeni-able confirmation during a six-month flight of the MarinerII spacecraft en route to Venus) and of the phenomenonof the coronal mass ejection first recognized as the highlydynamic process originating from the low corona in theearly 1970s (with the coronagraphs flown on OSO-7 andshortly after that on Skylab).Since those early observations, recent achievements inthe space-weather science arena are supported by an in-creased availability, accessibility, and sharing of both ar-chival and near-real-time space- and ground-based data.These involve, for example, the US “virtual observato-ries” for solar and for geospace data, and the InformationSystem of the World Meteorological Organization [WMO]through its Interprogramme Coordination Team on SpaceWeather [ICTSW] and the International Space Environ-ment Service [ISES], and the ICSU World Data Systemand World Data Center [WDS/WDC], and e-infrastructrueprograms in the EU (e.g., ESPAS, SEPServer, HELIO)and Japan (IUGONET), as well as by the development ofend-to-end modeling frameworks (including NASA’s CCMC),and various space agency programs (e.g., ESA SSA; NASAiSWA).On the solar side, we now have available continuousfull-Sun observations at multiple wavelengths, from mul-tiple perspectives, from below the surface into the helio-sphere. This observational coverage includes far-side ob-servations and stereoscopic imaging by STEREO, SDO,36nd SoHO combined with other observatories, and helio-seismic probing of the interior and even the far side of theSun. Unfortunately, this full-sphere coverage does not in-clude the (near-)surface magnetic field which is measuredonly from Earth’s perspective (continuously by SDO, andby some ground-based observatories). This full-Sun cov-erage supports the study of conditions leading to variablespace weather, including the evolution leading up to andfollowing solar storms, and the coupling to adjacent fluxsystems. But the space to cover is vast, and the observ-ables range in size scale, energy, wavelength, and otherphysical attributes over many orders of magnitude, requir-ing multiple types of observatories and necessarily leavinggaps in our knowledge.Years of increasing coverage and open-data policies haveled to a growing open-access event archival database ofwell-observed flares, CMEs, and particle events that en-ables event comparisons and inter-domain coupling stud-ies. Search and visualization tools are developing to in-crease the utility of and access to observational data. Onthe numerical front, leaps forward in the realism of numer-ical modeling that enable us to explore, for example, thegeneration, rise, and emergence of magnetic flux bundlesinto the solar atmosphere and the subsequent initial phasesof a CME, the formation of sunspots upon field emergenceonto the solar surface, and the analysis of chromosphericprocesses in a realm with radiative transfer, partial ioniza-tion, and comparable field and plasma forces. These nu-merical experimental settings are complemented by initialdevelopments of data-driven models of the solar coronalfield and of the Sun-heliosphere coupling in the nascentsolar wind.Within the heliosphere, we now have multi-perspectiveobservations of propagating disturbances from Sun to Earthand beyond, often as combinations of in-situ and remote-sensing observations. These include long-term, continu-ous, in-situ monitoring of solar wind and SEP proper-ties at the Sun-Earth L1 point, one million miles upwindfrom Earth, and multi-point, multi-scale measurements inthe near-Earth solar wind. These observations often pro-vide information on the structure of CMEs, including theshocks between CME and the preceding solar wind (it-self often containing earlier CMEs) that are important tothe generation of solar energetic particles (SEPs). It hasbeen demonstrated that approaching CMEs can be de-tected through interplanetary scintillation and that theseshow signatures in cosmic-ray muon intensities that maybe used as proximity proxies. Sets of spacecraft aroundthe inner heliosphere have demonstrated the prevalence ofwide-angle SEP events. Exploratory models exist of CMEpropagation, including CME-coronal-hole and CME-CMEinteractions, from near the Sun to beyond Earth orbit.Understanding of the magnetospheric dynamics greatlybenefits for the availability of continuous remote sensing ofsolar activity and in-situ L1 monitoring of solar wind andSEP properties. Many key advances in the research of en-ergy storage and release processes are being made owing to the availability of multi-point, multi-scale measurementsthroughout the magnetosphere (Cluster, THEMIS) as wellas specialist coverage of the magnetotail (ARTEMIS) andthe radiation belts (Van Allen Probes), and improved cov-erage by ground-based observatories (radar and magne-tometer networks, e.g., SuperDARN and SuperMAG). Here,as elsewhere in the science of Sun-Earth connections, sig-nificant advances in numerical modeling are made, includ-ing the coupling between CMEs and the geomagnetic fieldas well as magnetotail dynamics, based on developmentsthat utilize different approaches (magneto-hydrodynamic[MHD], hybrid, kinetic) and that include energetic par-ticles. Regional studies have improved understanding ofGIC effects at auroral latitudes and ionospheric impactsin the Southern Atlantic (magnetic) anomaly (SA(M)A-region). Although still challenging areas of research, ad-vances are being made in the characterization of substormdynamics (specifically their field evolution and system cou-plings), understanding of the ring current system, and ana-lyzing the importance of ionospheric feedback for geomag-netic field dynamics.In the ionosphere-thermosphere-mesosphere (ITM) do-main we see growing observational coverage and increas-ing regional resolution of ITM dynamics (including GNSSand ionosonde data), enabling near real-time maps of to-tal electron content (TEC) and critical-frequency maps forradio communication, and advances in 3D reconstruction(by, e.g., GNSS radio-occultation and Beacon receivers,AMISR, and forthcoming EISCAT 3D+ instrumentationand the Swarm mission). There is improved understand-ing of the contribution of the plasmasphere in the iono-spheric total electron content (TEC), especially on thenight side and during extreme events (e.g., plasmasphericplumes). Insight has been deepened in sub-auroral effects(e.g., SAPS), in vertical coupling between troposphere andionosphere (tidal modes, gravity waves), and in solar windmomentum storage and release in the thermosphere. Thereis improved access to data-product repositories, which inpart is due to empirical model development based on long-term databases. All this supports the development ofphysics-based models and understanding of the processesinvolved, including data-ingestion into assimilative mod-els, some of which are approaching transition to real-timeoperations.The rapid growth of observational and numerical re-sources is advancing our understanding of the Sun-Earthsystem as a coupled whole, but many major issues re-main to be addressed on the path towards improved scien-tific understanding and desired specificity in forecasts forthe various sectors of society that are impacted by spaceweather.
Appendix C.2. Prospects for future work
With regards to solar drivers of space weather, we haveto advance the diagnostic capability to forecast times, mag-nitudes, and directionalities of flares and eruptions; atpresent diagnostics with the best skill scores perform quite37oorly with often an unguided “no flare” forecast perform-ing best, and with trained observers unable to differentiateforecasts within 24-h increments and flare magnitudes un-certain to one or more orders of magnitude, and with onlythe first advances to forecast the magnetic content of erup-tions into the heliosphere being made in recent years. Newmagnetic field intruding into pre-existing active regions (aphenomenon referred to as “active-region nests” that onecould view as pre-conditioning) is often involved in ma-jor flaring, making even “all clear” forecasts difficult ontime scale more than about a quarter of a day. Long-range couplings and large-scale forces affect how erup-tions propagate into the heliosphere, and we face the prob-lem of limited coverage of solar magnetic field and coro-nal structure observations to incorporate within our grow-ing modeling capabilities: only little more than a quarterof the solar-surface is accessible for high-resolution, well-calibrated magnetography, with vector-field data routinelymade only for the active regions of their relatively youngearly-decay products.Another major challenge is establishing what deter-mines whether a solar event inserts SEPs into the helio-sphere and how such SEPs propagate through the helio-sphere. Advancing on these fronts requires the develop-ment of physics-based, data-based models for the researchcommunity, including in particular a general-purpose observ-ation-driven magnetic-field-modeling tool. Quantifying theproperties of extreme flares, CMEs, and SEP events re-quires investments in analyzing natural archives (e.g., bio-sphere, ice deposits and rocks - including those from the lu-nar surface; e.g., Kovaltsov and Usoskin, 2013), the use ofcool-star analogs to our Sun to capture a sufficient numberof rare extreme events to quantify the probability distribu-tion for such extreme events powered by our present-daySun. From a climatic point of view, we need to advanceour understanding of solar spectral irradiance variationsand its modeling based on magnetograms and models ofthe solar magnetic atmosphere.Once solar disturbances enter the heliosphere, we haveyet to understand what establishes the characteristics (width,direction, velocity), deflection, and propagation of CMEs,including the interaction with the background solar wind.That problem requires the development of data-driven MHDmodeling through general-access community models forthe background solar wind and for interplanetary CMEevolution from Sun to Earth (such as increasingly avail-able and supported at NASA’s CCMC). We have yet toestablish the properties of the 3D magnetic structure ofCMEs starting with CME initiation and following theirpropagation through and interaction with the magneticfield of the solar wind, required for forecasting CME ar-rival times and CME magnetic properties. Another majorissue is the understanding of shock propagation throughthe pre-existing solar wind and the resulting SEP produc-tion and propagation (distinct from the prompt relativisticparticles).Remote-sensing and in-situ observations are needed to validate heliospheric models, including continued in-situL1 monitoring of solar wind and SEP properties. We needto acknowledge, moreover, that the evolution of CMEs,and therefore their geo-effectiveness, is affected by the so-lar wind ahead of them: we need to include pre-conditioningof the heliosphere into account, and thus think in terms ofcontinuous evolution rather than in terms of isolated singleevents. On larger geometric and temporal scales, we needimproved understanding of how heliospheric magnetic fieldand solar wind modulate galactic cosmic rays, as well asimproved understanding of solar-wind patterns that cansignificantly enhance the energy of magnetospheric elec-trons. For the terrestrial magnetosphere, we need improve-ment of knowledge of conditions in the incoming solar windand incoming SEP populations, both by continued andimproved upstream monitoring and modeling/forecasting.At the ground-level “base” of the magnetospheric statewe need to ensure the continuity of global measurementsof electric field and currents by ground-based radars andmagnetometers and to find accurate methods to measurealso particle precipitation and consequent ionospheric con-ductance variations in global scales. The details of thesolar-wind/magnetosphere coupling remain elusive, so thatunderstanding of the geo-effectiveness of CMEs has to in-clude how the CME phenomena evolve through the bowshock. An additional challenge comes from magnetosphericpre-conditioning that can significantly modulate the im-pact of solar activity in the geosphere. Here, once more,we need physical data-driven modeling (MHD and kinetic)through general-access community models reaching acrossdipole-like and tail-like field domains, with ability to in-clude regional impact modeling and the forecasting of sub-storms, of auroral currents, of the ring current, and of par-ticle populations and their precipitation. We need multi-scale multi-component measurements in shocks, reconnec-tion, and turbulence, and understanding of cross-scale cou-pling from micro-scale physics to meso- and macro-scale.For particle populations in the radiation belts we needbetter understanding of energetic ion and electron injec-tion into radiation belts in storms and substorms, andalso better forecasting of solar-energetic particle radiationstorms at LEO and aircraft altitudes. Coupling acrossdomains is also important, requiring space-based multi-point exploration of the MIT interfaces to understand,e.g., the origin of outflow ions and their roles in the mag-netic storm development and the characteristics of theionospheric-thermospheric phenomena caused by magneticstorms. Lacking natural records, the specification of worst-case magnetospheric processes leading to strong GICs willrequire physics-based models, to be somehow adequatelyvalidated for conditions not normally encountered in geo-space.A key goal, perhaps the key goal, in mitigating spaceweather impacts mediated by the ionosphere is to develop3D global models of the morphology of the ionosphere.Given such a model it will then be straightforward to de-rive many products needed by users, e.g., nowcasts and38orecasts of TEC for GNSS and space radars, of usable fre-quencies for HF communications (e.g., foF2, MUF(3000)F2)and of where there are strong spatial gradients that willlead to ionospheric scintillation. Such models must bephysics-based in order to encompass all the processes andphenomena that can affect the morphology of the iono-sphere, especially in highly disturbed conditions. Theymust therefore include coupling to all the systems asso-ciated with the ionosphere, especially the co-located neu-tral atmosphere (thermosphere) as well the magnetically-coupled regions of the plasmasphere and magnetosphere.The key processes to be studied include the coupling ofsolar-wind-magnetospheric variability, ion-neutral coupling,the development and evolution of ionospheric storms, trav-eling ionospheric disturbances (TIDs), small-scale irregu-larities and bubbles, the mechanisms behind equatorial F-region radio scattering, and the role of small-scale struc-ture in the mid-latitude ionosphere. An adequate un-derstanding of all this necessary physics requires extend-ing coverage of these coupled domains by globe-spanningground-based networks for continuous observation (includ-ing mid- and low-latitude electron and neutral density,electric field, and neutral wind variations during geomag-netic events). Coordination in the development of thesenetworks is also needed, including integration of ground-and space-based data systems, to develop data-driven mod-eling capability for the near-real-time ionospheric mor-phology. In this domain, too, we identify how physicaldata-driven modeling feeds into general-access communitymodels for, e.g., regional perturbation knowledge, includ-ing scintillation, and near-term TEC forecasting. ITMstudies will also feed into improved predictions of satel-lite drag for the purpose of orbit calculations (includingcollision avoidance, scheduling of critical operations andre-entry predictions) via better modeling of the thermo-spheric neutral density, temperature and composition.Finally, we note that there is much synergy with radioastronomy. Many ionospheric processes add noise to radioastronomy observations, so there is scope for sharing ofdata and knowledge on the basis of one scientist’s noiseis another’s signal. In addition, the technologies beingdeveloped for advanced radio telescopes (e.g., LOFAR andthe Square Kilometer Array SKA) have great potentialfor spin-out into ionospheric work, e.g., as demonstratedby the Kilpisj¨arvi Atmospheric Imaging Receiver Array(KAIRA) in Finland. Thus the ITM space weather thecommunity needs to strengthen the links with the radioastronomy community in this exciting new era.
Appendix D. Research needs for the solar-heliosphericdomain
In this Appendix D, and in the subsequent Appendix E,we provide a series of needs derived from detailed formu-lations of the top-level goals. In specifying the needs, wedifferentiate between data that we require to enable the ba-sic process and data that we desire to significantly improve our ability or to accelerate our progress. We also differen-tiate between observables that are already being obtainedand which we need to maintain, and observables for whichwe need to improve instrumentation or diagnostic capa-bility, or observables for which we need to develop newcapabilities. Priorities in this Appendix are given for thescience of the solar-heliospheric domain; they are mergedand renumbered with the priorities from the geospace do-main from Appendix E in the main text of this roadmap.
Goal SH-1: Time-dependent description of the coronalmagnetic field, both for the space-weather source regions(i.e., quiet-Sun filament environments and active regions)and for the embedding global field.
The cornerstone of any understanding or prediction ofsolar activity lies in the magnetic field. We note that • the three-dimensional magnetic field of an eruptingregion and of the surrounding corona are essential forspecifying the characteristics of the transient solaractivity that causes space weather impacts; • the magnetic structure of the solar ejecta and itsinteraction with the embedding coronal and helio-spheric fields result in the strength and orientationof the changing magnetic field that will reach theEarth; and that • the coronal magnetic field and its extension into theheliosphere affect SEP creation and transport. Goal SH-1a: Specify magnetic structure of space-weathersources associated with active regions • REQUIRE: High-resolution vector photospheric fieldand plasma flow boundary condition. MAINTAINthe ability (SDO/HMI) to observe the full disk atabout 1 arcsec resolution. IMPROVE for source re-gions by an order of magnitude spatially to at least0.3 arcsec resolution as combined 2nd priority by newsolar observations (as envisioned, for example, forSolar C). • REQUIRE: Vector boundary condition at a force-free layer, e.g., the top of the solar chromosphere.IMPROVE on the current ground-based experimen-tal ability at NSO/SOLIS and MLSO ChroMag; NEWability to be developed for space-based observationsat about 0.2 arcsec resolution as combined 2nd pri-ority by new solar observations (such as planned forSolar C), along with extensive theoretical/modelingdevelopments. • REQUIRE: Development and validation of algorithmsfor magnetic field models using, e.g., coronal po-larimetry and imaging data, including considerationof connections between active region magnetic fieldsand the surrounding global background coronal field.IMPROVE on current modeling capabilities in MHD39nd nonlinear force-free codes using currently avail-able (e.g., SDO) observations [MAINTAIN] at about1 arcsec resolution. NEW: combine with informa-tion from radio gyroresonance measurements (FASR,CSRH). • REQUIRE: Off-Sun-Earth line observations of thecoronal plasma structures for on-disk source regionsof solar eruptions. Develop a NEW capability toobtain and ingest binocular observations from near-Earth perspective and at about 10-20 degrees offSun-Earth line as 1st priority in solar observationswith a new mission concept.
Goal SH-1b: Specify the evolving global background coro-nal magnetic field: • REQUIRE: Full-disk, front-side photospheric bound-ary condition. MAINTAIN the ability to obtain full-disk magnetograms as now possible with SDO/HMIand some ground-based observatories (GBOs). • REQUIRE: Models for the global solar field reachinginto the heliosphere are crucially limited by mag-netograph data being available only for the Earth-facing side of the Sun. More comprehensive bound-ary data for a significantly larger portion of the so-lar surface, especially near the east limb of the Sun(where data obtained from Earth-based observationsis oldest as regions evolve on the far side) is neces-sary. This may occur through incorporation of in-formation from the backside of the Sun as seen fromEarth, via helioseismology/time-shifted data and/orby direct observations off the Sun-Earth line of thephotospheric field, specifically at least about 50 he-liocentric degrees trailing Earth (from around an L5perspective, or - at least for some time - with theSolar Orbiter mission). IMPROVE modeling com-bined with NSO/GONG and SDO/HMI helioseismo-logical data. NEW: 3rd priority capability of solarmagnetography off the Sun-Earth line, at first withthe Solar Orbiter, while planning for sustained suchobservation for more extensive coverage in the moredistant future. • REQUIRE: Calibration of the high-latitude magneticfield (using, e.g., measurements from above and be-low the ecliptic plane) to validate surface flux trans-port models for the largest-scale field that deter-mines the overall heliospheric structure. IMPROVEmodeling combined with high-resolution observationsfrom, e.g., Hinode and GBOs; obtain observationalcoverage of the high-latitude regions by the out-of-ecliptic observatory Solar Orbiter as 3rd priority inNEW solar observations. • DESIRE: Full-disk, chromospheric magnetic bound-ary to validate and constrain magnetic models; the first step should be a study to establish the poten-tial value of full-disk chromospheric vector magne-tographs as addition to surface field measurements;NEW measurements under development by MLSOCOSMO and planned for Solar C. • DESIRE: Coronal polarimetry (radio, infrared, visi-ble, UV) to validate and constrain magnetic models.A first step here is to IMPROVE our abilities to usepresent-day GBO data to guide and validate contin-uous MHD field modeling of the global solar corona. • REQUIRE: Coronal imaging to validate and con-strain magnetic models. MAINTAIN the ability toobtain X/EUV imaging of the solar corona with space-based observatories at about 1 arcsec resolution asnow possible with SDO, supported by STEREO.
Goal SH-1c: Evolving description of the ambient inner-heliospheric magnetic field and plasma flow in the solarwind through which CMEs propagate and with which theyinteract, that is important for the generation and prop-agation of energetic particles, and that drives recurrentgeomagnetic activity. The foundation of such models isderived from Goal SH-1b. • REQUIRE: Data-driven modeling of the solar windthroughout the inner heliosphere, improved with bet-ter descriptions of underlying physics, and routinelyincorporating magnetic field to go beyond present-day hydrodynamic modeling. MAINTAIN the abil-ity to feed coronagraphic observations into heliosphericmodels, but substantially IMPROVE the modelingby including magnetic information from the coronaand advancing it towards geospace and beyond. • REQUIRE: Development of techniques to adjust mod-els based on heliospheric observations, including avail-able heliospheric images, and the development ofNEW tools, such as radio-based interplanetary scin-tillation (IPS) methods, to detect and map pertur-bations approaching Earth. • DESIRE: Solar and interplanetary observations fromabove the ecliptic plane to validate models or toguide models once such capabilities are developed.Such NEW observations could for some time be pro-vided by the Solar Orbiter, the 3rd priority solarinstrumentation, to develop and evaluate the utilityof such observations. • DESIRE: Continuation of multi-view, multiple EUVemission line, full-disk photospheric vector magne-tographs, multi-view coronagraphs and heliosphericimaging, and L1 solar wind measurements. Thesecapabilities should be MAINTAINed to drive mod-eling.
Goal SH-1d: Specify magnetic structure of space-weathersources associated with long-lived (quiescent) filaments REQUIRE: Observations of the photospheric line-of-sight boundary condition. MAINTAIN the abil-ity to obtain full-disk magnetograms, such as nowobserved by SDO/HMI and GBOs. NEW: a capa-bility to cover more of the solar surface for magneticmeasurements as 3rd priority. • REQUIRE: Characterization of coronal currents us-ing non-potential magnetic models, and/or coronalevolution models, that are validated/fit to data suchas coronal polarimetric (radio, infrared, visible, UV)and imaging observations. IMPROVE our abilitiesto used space and ground-based imaging and GBOpolarimetric observations to guide and validate mag-netic modeling capabilities based on MAINTAINedsurface field maps. IMPROVED and NEW coro-nal polarimetric measurements under developmentfor GBOs in the U.S. and China, and potentially offSun-Earth line. • DESIRE: Chromospheric magnetic field (boundarycondition and prominence) measurements to validateand constrain magnetic models. IMPROVED/NEWGBO observations and data assimilation techniques. • DESIRE: off-Sun-Earth line observations of coronalplasma; this NEW ability, the 1st priority for solarobservations, is to be combined with NEW data as-similation techniques.
Goal SH-2: Description of CME/flux-rope evolutionthroughout the heliosphere, enabling prediction of CME ar-rival time, kinematics, and magnetic field strength and di-rection as function of time.
Once the plasma and magnetic properties of the ejectafrom the solar source regions are specified, we are in aposition to determine its heliospheric evolution. We notethat • quantitative knowledge of the properties of the erupt-ing field and the field into which it erupts enablemodeling of the transport and evolution of that erup-tion throughout the heliosphere en route to Earth; • specifying the solar wind conditions incident uponthe magnetosphere is critical for determining the spaceweather response in the geospace system; and that, • in particular, high-impact hazards of space weatherstrongly depend on the strength and orientation ofmagnetic fields and the density and velocity at solarwind at the Earth. • REQUIRE: NEW data-assimilative models couplingcoronal models to solar wind propagation models (innear-real-time), explicitly incorporating magnetic fluxrope structure established from Goal SH-1a and 1dinto background wind model (Goal SH-1c). • REQUIRE: MAINTAIN/IMPROVE on validation ofsolar-wind propagation models with in situ observa-tions at Earth/L1. • DESIRE: MAINTAIN/IMPROVE validation of solar-wind propagation models with off-Sun-Earth-line in-situ observations (STEREO) and NEW off-Sun-Earthline remote-sensing observations (e.g., L5) and above-ecliptic (Orbiter, SPP). • DESIRE: MAINTAIN/IMPROVE on validation ofsolar-wind propagation models with remote imaging:e.g., Heliospheric imagers (structure), muon detec-tion (orientation via pitch angle anisotropy), radio(Faraday rotation measurements constrain magneticfield strength), IPS.
Goal SH-3: Develop the capability to predict occurrenceof transient solar activity and the consequences in the he-liosphere
Given the coronal magnetic field, we are in a positionto characterize and predict solar drivers of space weather.We note that • transient solar activity leads to a conversion of mag-netic energy into space-weather-driving phenomenasuch as flares, coronal mass ejections, and energeticparticles; • interactions between the space-weather source andthe global background corona affect the propertiesof these phenomena; and that • the ability to predict transient solar activity in ad-vance is generally desired, and required for warningof prompt solar energetic particles Goal SH-3a: Predict transient solar activity in advance • REQUIRE: MAINTAIN observations that may beused for precursor warnings, e.g., active-region com-plexity, neutral-line shear, filament activation, helio-seismology obtained from a range space and ground-based observatories, and IMPROVE upon theoreti-cal and empirical justifications and implementationstrategies for their use. • REQUIRE: Develop NEW capabilities for ensemblemodeling in which probability of eruption is obtainedbased on perturbing coronal magnetic structure de-termined as in Goal SH-1, through e.g., flux emer-gence/flows, with consideration of sympathetic erup-tive likelihood. • DESIRE: IMPROVE on theoretical understandingand modeling capability for predicting instability byanalyzing the topological properties of coronal mag-netic structures determined as in Goal SH-1.41
DESIRE: MAINTAIN STEREO observations thatmay be used for precursor warnings using off-Sun-Earth-line observations; NEW off-Sun-Earth line ob-servations.
Goal SH-3b: Specify the consequences of transient solaractivity into the heliosphere • REQUIRE: MAINTAIN space and ground-based multi-wavelength imaging (including coronagraph) duringeruption including Sun-Earth-line (SoHO, SDO), off-Sun-Earth-line (STEREO), and NEW off-Sun-Earthline observations. • REQUIRE: IMPROVE on existing techniques to quan-tify kinematic properties of ejecta including velocityand trajectory • REQUIRE: IMPROVE on eruptive models startingfrom coronal magnetic structure determined as inGoal SH-1; NEW incorporate interactions betweenthe source and the background during eruption, andconstrain/validate by data - leading to quantificationof magnetic structure of ejecta.
Goal SH-4: Prediction of particle intensities, includingall-clear forecasts, flare-driven acceleration near Sun, andshock acceleration at CME fronts.
Energetic particles present a major hazard to space-based assets as well as possible consequences for aircraftand aircrews and aircraft passengers, particularly in polarroutes. The production of SEPs is associated with largeflares and fast CMEs in the low corona, typically origi-nating from complex active regions. The prompt-responseparticles can arrive at Earth in less than an hour (sometimes as rapidly as a few minutes) after the onset of aneruption. These prompt SEPs may be followed by a longerlasting flux of particles originating at the CME shock asit propagates through the heliosphere, and a short, sharp,very high flux of energetic storm particles (ESPs) as theCME shock passes the point of measurement. Many ofthe needs to improve understanding of the prompt SEPsand ESPs are contained in the needs for solar and inner-heliospheric phenomena; the purpose of this short sectionfocusing on SEPs and ESPs is to explicitly highlight theirsignificance.The strong increases in fluxes of high-energy protons,alpha particles and heavier ions in SEP events can causeor contribute to a number of effects, including: • Increases in astronaut radiation doses resulting inincreased long term cancer risk and short term inca-pacitation • Single Event Effects (SEEs) in micro-electronics • Solar cell degradation • Radiation damage in science instruments and inter-ference with operations • Effects in aviation include increases in radiation doselevels and interference with avionics through SEEs.While warning of events in progress is certainly impor-tant, many user needs (e.g., all-clear periods for EVAs forastronauts) require significantly longer warning, e.g., 24hours.
Prompt energetic particles vs. energetic storm particles.Prompt particles:
At the onset of major (M or X-class)flares and CMEs, SEPs can arrive in minutes after the startof the event. These events are typically associated withlarge, magnetically complex active regions. The energysource of the particles is still under debate: it may beentirely due to shocks generated low in the corona, or itmay be that reconnection in solar flares plays a vital role,or both. The prompt SEPs represent the most difficultforecasting problem, as they require • The prediction of major solar flares and eruptionsprior to their occurrence. • The efficiency of the flare/CME to produce energeticparticles • The escape conditions of the particles from the coro-nal acceleration site • The angular extent for injection of particles in theinterplanetary medium (STEREO observations showthat prompt energetic particles can be measured ona wide longitudinal extent). • The conditions of propagation of the prompt parti-cles in the interplanetary medium (a large proportionof SEP events are found to propagate not along thenormal Parker spiral but in the magnetic field of aCME). In addition to the conditions of diffusion inthe medium, this evidently affects the delay betweenproduction of energetic particles and arrival at theearth.
Energetic Storm Particles (ESPs):
Energetic storm par-ticles are particles detected in situ when shocks pass byspacecraft. These are particles trapped by turbulence justahead of the shock front, and can be prominent eventswith the particle flux jumping by 1-2 orders of magnitude.Occasionally, ESPs can reach >
500 MeV and hence posemajor space weather hazard. Therefore, the ESPs repre-sent a “delayed” radiation hazard because the ESP eventforecast is essentially a shock arrival forecast. The dura-tion of the ESP event generally depends on the shock ge-ometry: At quasi-perpendicular shocks (where the shocknormal vector is perpendicular to the local magnetic field),generally a narrow spike is observed, while a broad profileis observed in a quasi-parallel shock.42 good indicator of an impending ESP event is a radio-loud shock, i.e. a shock that produces type II radio burstnear the Sun. Stronger shocks generally produce moreintense ESP events. Radio-quiet shocks can also produceESP events. Shock travel time ranges from about 18 hoursto a few days, so there is a good chance of making predic-tion of ESP events.ESP events events precipitate in the polar regions andthus they are hazardous to satellites in polar orbits. Theylead to radio fadeouts in the polar region and may causecommunication problems for airplanes in polar routes.Understanding and predicting particle acceleration re-lies on all preceding SH goals. We note that • Given a heliospheric field description, connectivityof Sun to Earth can be determined enabling all-clearforecasts if no active region is connected to the Earth(thus, even if flaring occurs, prompt particles on timescales of 10s of minutes are unlikely to occur). How-ever, there are unsolved problems related to unusualspread of SEPs in longitude. • Given prediction of a flare/CME, warning may begiven of prompt particles and generally of SEPs ontime-scales of 1-2 days; information about connec-tivity combined with models/observations may givewarning of their likely geoeffectiveness. • CME driven shocks continuously accelerate particlesfrom the corona to 1 AU and beyond, so once aCME occurs, models that propagate them throughthe background heliosphere may predict shock-relatedSEPs, and in combination with observations of shockscan allow prediction of geoeffectiveness.
Goal SH-4a: All clear (ongoing) • REQUIRE: IMPROVE/NEW Evolving heliosphericmodel driven by 3D coronal field model (Goals SH-1b and c). Modeling/analysis to understand un-usual longitude spread and prompt rise of some SEPevents. • DESIRE: IMPROVE/NEW Predictive models of erup-tion, analyzed in the context of global field, to es-tablish likelihood of connectivity change and sympa-thetic eruptions (Goal SH-3a).
Goal 4b: Predict Rapidly Arriving SEPs (time scaleminutes to hours) • REQUIRE: MAINTAIN/IMPROVE nowcast obser-vations to predict geoeffectiveness of incoming SEPs:relativistic and mildly relativistic particles (neutronmonitors and GOES) to establish connectivity andforewarning of future, less energetic particles; mea-surement of type III radio bursts to establish thatthe flare/eruption site has access to open magneticfields. • REQUIRE for 1-2 day forecast: IMPROVE/NEWability to predict flares/CMEs (Goal SH-3a). • DESIRE: IMPROVE/NEW Evolving heliosphere modeldriven by 3D coronal field model (Goal SH-3), cou-pled with particle acceleration models and proba-bilistic/stochastic methods to characterize likelihoodof strong SEPs from an active region.
Goal 4c: Predict SEPs from shock acceleration/transport(time scale hour to days) • REQUIRE: MAINTAIN radio observations of TYPEII bursts indicating shocks in front of CMEs; GBOradio observations to provide information on shocksclose to the Sun at high frequency; L1-observationsof shocks driven in interplanetary space that must bemeasured from space because they are below iono-spheric cutoff • REQUIRE: MAINTAIN in situ measurements of SEPsat L1. • DESIRE: IMPROVE/NEW evolving heliosphere modeldriven by 3D coronal field model with treatment ofresponse to propagation of CME (Goal SH-1b andc), coupled with particle acceleration and transportmodels. • DESIRE: MAINTAIN/NEW multi-point in situ mea-surements of SEPs off Sun-Earth line (STEREO, So-lar Probe Plus, Solar Orbiter).
Appendix E. Research needs for the geospace do-main
Following our impact tracings for the three differenttechnologies presented earlier in this roadmap, we catego-rize the scientific activities as follows: • Magnetospheric field variability and geomagnetically-induced currents; • Energetic particles, in order of impact importance: – Solar energetic particles, – Radiation-belt energetic particles, and – Galactic cosmic rays; • Ionospheric variability.
Appendix E.1. Magnetospheric field variability and geo-magnetically-induced currentsGoal GM1: Understand the dynamical response of thecoupled geospace system to solar wind forcing to improveGIC forecast capabilities
Goal GM-1a: Understand energy storage and release inthe MIT system in driving large dB/dt at ground. • REQUIRE: Goal oriented research for improved phys- ical understanding of the onset of rapid and largescale magnetotail morphology changes, including sub-storm onset, for improved physics-based forecasting(5th priority in Pathway I recommendations for mod-eling). At the moment we only see that some timesthe magnetosphere decides to deliver the excess en-ergy to the ionosphere in a steady flow or smallparcels (e.g., in the form of BBFs in the tail), andsome times in one big parcel (substorm), drivingGICs. We need to find out which characteristic ofthe coupling or which characteristic of the driver de-termines this choice. In addition, we need improvedunderstanding of the role of preconditioning in de-termining the magnetospheric response to a time se-quence of solar wind drivers (cf., the largest ever his-torical super-storms have occurred as isolated eventswhich can (often) be during solar minimum periods). • REQUIRE: Systematic observations characterizingthe global state of the MIT system (3rd priority inPathway I recommendations for new instrumenta-tion). Such observations require a maintained fleetof spacecraft in crucial locations in the tail and closeto the ionospheric end of the conjugated field linesas described in section 7c. In addition, in order tosolve the remaining key physics questions, we willrequire 2 constellation type missions at locations atthe inner edge of the plasma sheet (from 7-12 R E ),and within the so-called auroral acceleration regionat several thousand km altitude. None of these satel-lites needs radically new and expensive instrumenta-tion though. The challenge lies in populating the keylocations with spacecraft housing standard plasmainstrumentation suites, and designing orbits whichoptimize the presence of s/c at these locations oftenenough, if not continuous. Again, the THEMIS mis-sion provides some useful perspectives for the plan-ning of the necessary configurations of future fleets orconstellations. It would be valuable to have simulta-neous measurements from both inside and outside ofthe onset region (at it’s Earth side and further in thetail) in order to follow energy conversion processesand associated plasma flows towards the Earth andaway from the magnetotail in the form of plasmoids.In addition a set of 4-6 probes at geostationary dis-tances and distributed evenly in different MLT sec-tors would help in understanding how a major parti-tion of this released energy gets stored into the ringcurrent and radiation belts. An important asset sup-porting these missions would be a set of LEO satel-lites with magnetic field and particle instruments inorder to get a better handle on the magnetosphere-ionosphere coupling (energy carried by currents andprecipitating particles). A particular challenge is tomeasure the intensity of field-aligned currents thatdirectly control the horizontal currents in the auroralionosphere and consequently also the dB/dt values44s measured on the ground. NEWMAINTAIN: When planning satellite fleets or con-stellations for probing the MIT system it is impor-tant to keep in mind the support that other existingsatellite missions can provide. A nice example to-wards this direction is the AMPERE project whichmaintains an impressive set of magnetometers hostedby the Iridium satellites on LEO orbits. Another ex-ample of fruitful collaboration with long heritage ofsupport to other space plasma missions is the DMSPprogram hosted by the United States Department ofDefense. Ensuring continuity of this kind of missionswill be an important factor in the attempts to keepthe costs of multipoint MIT-monitoring on a tolera-ble level. • REQUIRE: With the help of observations describedabove we need to develop magnetospheric modelingcapacity taking upstream solar wind input and deriv-ing forecast dB/dt at the Earth‘s surface, includingtransformation and coupling at the bow shock andthe magnetopause, coupling between hot and coldmagnetospheric plasma populations, and couplingto the ionosphere including ionospheric conductiv-ity modules and feedback (5th priority in PathwayI recommendations for modeling). We have still lit-tle understanding on the relative importance of suchpre-states in the prime coupled elements of our sys-tem, nor the time constants of their potential im-pacts, but they are in order of distance from theEarth: – Atmosphere: temperature, altitude/density andwinds - long lived (a day or so) – Ionosphere: conductivity and convection (strengthand location) - short lived (from seconds to hours) – Plasmasphere: location and density - long lived(days) – Ring current: strength, composition, energy ofparticles, shape and/location - long lived (days) – Tail current: strength, mass composition, tem-perature, shape and/or location - short lived(hours) – Lobe field: pressure from previous energy cou-pling to solar wind, i.e. the energy reservoirfrom previous events is not completely emptied- no intrinsic time constant, influenced by othersystem input and output. • REQUIRE: Coordinated ground-based measurementcan provide crucial support for satellite missions (6thpriority in Pathway I recommendations for main-taining existing capabilities). We propose to estab-lish a formal basis for collaboration and data shar-ing between heliospheric and magnetospheric mis-sions and ground-based assets. Informal (e.g., Clus-ter Ground-based Working Group) and formal (e.g., THEMIS mission) agreements have been made be-fore, but usually missions do not involve a require-ment for GB support in their level-1 science require-ments for ground-based support (Van Allen Probes,MMS, Solar Probe, etc). This must be rectified.Satellite missions require support from a global net-work of – MAINTAIN/IMPROVE: ground-based magne-tometers, for the global and local current pat-terns. Instruments operated in the auroral zoneand polar cap (magnetic latitudes above about65 degrees) yield often the most interesting data,but during storm periods also sub-auroral sta-tions (magnetic latitudes of some 55-65 degrees)are needed for grasping the entire picture. Ac-cording to the recommendations of the WMOInterprogramme Coordination Team on SpaceWeather (WMO/ICTSW) the threshold for spa-tial resolution in ground-based magnetic fieldrecording is 500 km for SWx monitoring whilefor breakthrough science it would be ∼
100 km . – MAINTAIN/IMPROVE: radars for the electricfield and convection patterns on meso-scale. Onglobal scale such measurements can provide in-formation on the energy state of the magneto-sphere from oval size and dynamics. Similarlyas for magnetometers, the interesting magneticlatitudes are mostly above 55 degrees. WMO/ICTSWrecommendations for spatial resolutions are 300 kmand 10 km for monitoring and break-throughscience, respectively. – NEW: optical monitoring from space or groundfor the precipitation and conductivity state (7thpriority in Pathway I recommendations for newinstrumentation). While ground-based instru-ments (all-sky cameras) are useful in the re-search of meso-scale physics, again as in thecase of radars for system level science global im-ages by space-born imagers will be of key impor-tance at least for two reasons: i) Space-basedobservations do not suffer from cloudiness prob-lems and ii) global scale instantaneous imagesof the auroral oval provide valuable informationon the magnetospheric energy storage and re-lease processes during storm and substorm pe-riods. • DESIRE, IMPROVE/NEW: Improved magnetosphere-ionosphere coupling models, including the impactof feedback between field-aligned current structuresand energetic particle precipitation on ionosphericconductivity - which is an important aspect of thecreation of ionospheric currents and hence grounddB/dt, resulting in an electric induction field. DESIRE, IMPROVE/NEW: Improved data assim-ilation method and models applied to the coupledmagnetospheric system including magnetic fields, cur-rent systems, and hot and cold plasma populations. • DESIRE, IMPROVE: Capacity to specify the globalstate of the magnetosphere will ultimately be re-quired to advance our knowledge of space weather tothe true point of predictability. Even with currentlyoperating multi-satellite missions in the so-called He-liophysics Great Observatory, geospace remains ex-tremely sparsely sampled in-situ. Global networksof ground-based magnetometers, radars, and opticalimaging (both ground and space) provide the onlycurrently credible approach to specifying the globalstate of the coupled magnetosphere ionosphere sys-tem. Even supplemented by current satellite mis-sions, the state remains sparsely specified in the crit-ical regions of in-situ geospace.Future efforts to develop nano- and micro-satellite in-frastructure could offer a cost-realistic route to a true con-stellation class mission (perhaps 50-100 satellites) neededto advance the system level science beyond its current typi-cal case study methodology. Hosted payloads may offer anadditional attractive route to securing constellation classspecification of the state and dynamics of the in-situ geo-space environment. Note, however, that this would be onlyan additional and not alternative route, as those instru-ments would most likely have to rely on simple measure-ments of plasma characteristics and relatively coarse and“dirty” field measurements due to host instrumentationinterference. Nevertheless to monitor simple arrival timesof changes in the plasma environment these would still bevery valuable for science, but more so for monitoring. Suit-able missions, which could host SWx instrumentation are,e.g., Galileo satellites, meteorological satellites on polarand geostationary orbits, and satellites testing new spacetechnologies (e.g., the PROBA missions). Keeping theseopportunities in mind, new SWx instrumentation shouldbe based on generic solutions with are suitable for payloadshosted by several different missions. NEW
Goal GM-1b: Understand the solar wind - bow shock -magnetosphere-interactions • REQUIRE, MAINTAIN/IMPROVE/NEW: Ongoing,reliable and continuous upstream monitoring of in-coming solar wind conditions and propagation to1AU such as from L1, or from other locations closerto the sun (4th priority in the Pathway I recommen-dations for maintaining existing capabilities).A suitable solar wind monitoring capability will berequired. Data from L1 typically gives the generalidea and this location is definitely suited for the pri-mary mission for SWx forecasts, but in the near fu-ture we will also need satellites closer to the subsolarbowshock/magnetopause to understand what really arrives at Earth. For such remaining science pur-poses during the years 2007-2009 a good constella-tion was formed by the Cluster and THEMIS multi-satellite missions. Systematically during spring andautumn times one of these missions was monitoringthe energy feed from solar wind and the other wasprobing the consequences in the magnetosphere. En-suring such coordination between different missionswill be vital for better physical understanding of en-ergy transfer processes between solar wind and mag-netosphere. In longer run the research conductedwith Cluster-THEMIS (or in the future MMS-Cluster-ARTEMIS) observations should pave the way to de-sign future cost-efficient solutions for continuous mon-itoring of upwind conditions with optimally config-ured satellite constellations.Both Cluster and THEMIS have been designed forscience purposes. For SWx monitoring a less com-prehensive suite of instrumentation would most likelybe sufficient. A basic set of instrumentation could in-clude, e.g., magnetic and electric field (at least ACin the case of E-field) instruments and a plasma in-strument(s) with similar specification as in Cluster(e.g., electron and ion spectrometers, energy ranges1 eV - 30 keV). The combined THEMIS and Clusterconstellation provides a good first basis for examin-ing the baseline for future constellations, for observ-ing the time evolution of solar wind structures asthey cross the bow shock, magnetosheath and mag-netopause regions (mainly for case study purposes). • DESIRE, IMPROVE/NEW: Improved global kineticand/or hybrid models of the solar wind-bow shockmagnetosphere interaction, including1. downstream impacts of kinetic bow shock andmagnetosphere processing of upstream solar wind,2. development and improved coupling of kineticmodules into global magnetospheric models es-pecially plasmasheet-ring current-magnetosphere-ionosphere system. • DESIRE, NEW: Research in order to achieve a con-solidated view whether a satellite (or satellite con-stellation) located closer to the Sun-Earth line thancurrently at L1 is crucial to get better GIC predic-tions or not. Previous studies presented in the liter-ature give a controversial view about this question.As a consequence it is at present not clear: – how close to the Sun-Earth line does a mon-itor need to be to get good upstream condi-tions for space weather/GIC input (in the lit-erature the correlation length is different forthe magnetic field, for the plasma velocity, andfor electric field/potential (Burke et al., 1999);this knowledge determines whether an L1 or-bit (perhaps constrained to within 60 R E only)46s good enough or whether observations directlyupstream from, and close to, the Earth on Earthorbiting spacecraft or constellation of spacecraftis needed. – whether we can specify what we need in termsof SW parameters with a single satellite andsome assumptions about field orientations toconstrain it (Weimer and Kind 2008); or whetherwe would rather need multi point measurementsin the upstream solar wind for improved predic-tions. Goal GM2: Uncover patterns in geomagnetic activityassociated with disturbances in, and failure modes of thepower grid infrastructure. • GICs have potentially the largest space weather im-pacts on terrestrial infrastructure, with potentiallylong lasting and very severe impact and the modesof impact and consequent failure risk need to be un-derstood. • Models of the impacts of imposed dB/dt from thecoupled geospace system in the form of geoelectricfields on power grids need to be developed and im-proved, and the effects arising from underlying solidearth physics such as sub-surface and sea-water con-ductivity should be included.To date our understanding of the temporal and geo-graphical patterns of geo-electric fields that are the mosteffective in driving GIC impact on the hardware in, or theoperation of, electric power grids is very limited.
Priority: Develop the tools and data needed to enableengineering and impact studies to understand the failuremodes of power grids in dependence of GMD driver char-acteristics.Goal GM-2a Understand the factors controlling the geo-electric field in the regions of primarily critical power grids,i.e serving dense populations at latitudes typically sufferingfrom large GMDs. • REQUIRE: MAINTAIN/IMPROVE/NEW: Deploy-ment of a network of ground-based magnetometersand magnetotelluric instrumentation for geo-electricfield measurements with infrastructure for data col-lection and distribution in near-real time. The crit-ical density of real-time magnetometer and magne-totelluric networks needed for the regions of criti-cal power grids under the risk of SWx disturbancesshould be defined on the basis of knowledge aboutunderlying gradients in ground conductivity in therelevant regions, as these may cause very localizedfeatures in the geo-electric field. • REQUIRE, IMPROVE/NEW: Systematic studies onground-conductivity in the regions of high GIC risk. Combining results from ground-based, air-borne andsatellite (Swarm in particular) measurement cam-paigns including both solid-earth and sea-water con-ductivity effects.
Goal GM-2b: Assess and access space weather GIC riskand impact data. • REQUIRE, IMPROVE/NEW: Make power grid GIC(current and electric field) data available to the widerspace weather research community (c.f. General rec-ommendations for collaboration between agencies andcommunities, point i). Data of actual GICs effectsin power grids are often collected by grid operators,but such data are for a variety of reasons often not(easily) made available for the scientific and techni-cal study of risks, except internally with the powergrid companies. This kind of data will be essen-tial in the efforts to gain improved understanding ofthe different modes of malfunction (non-linear be-havior, extra harmonics, and heating, overload etc)of transformers and power grids under GIC forc-ing. For space weather purposes this is particu-larly important as the scientists do not always knowwhich type of disturbance is actually leading to po-tentially damaging impacts on various critical partsof the power grid infrastructure. This requirementincludes therefore also determining the characteris-tics of the most geo-effective time sequences of dy-namic fields (one large event, or a fluence of manysmaller repetitive or pulsating events or persistentmoderate forcing) and their impact on infrastruc-ture spanning from individual single transformer fail-ure and lifetimes to catastrophic network collapse.Knowledge of such impact factors could both im-prove the relevance of space weather predictions (notonly large dB/dt warning required) and assist in theindustries own assessments of approaches to criticalinfrastructure protection (CIP) through design of re-silient power networks avoiding design with singlepoint failure under the expectation that some ele-ments of the network will likely fail. • REQUIRE, IMPROVE/NEW: Nations should con-sider undertaking a vulnerability and risk assessmentfor space weather impacts on their power grids andother infrastructure, recording the resulting risks innational Risk Registers and adopting appropriate pol-icy and taking appropriate action to mitigate suchrisks.
Appendix E.2. Magnetospheric field variability and parti-cle environment
The energetic particle environment in the magneto-sphere is an important factor of space weather. The mainexternal sources of the magnetospheric energetic particlepopulation are SEPs and GCRs, as well as solar wind47lasma particles. The last ones, being accelerated by mag-netospheric processes, are responsible for radiation belts,auroral FACs and particle precipitation into the upper at-mosphere. The dynamics of the magnetospheric magneticfield under solar wind driving controls particle distribu-tion, acceleration and losses. We note that: • Solar activity is the main controlling factor for theparticle environment in the Earth’s magnetosphere. • Active processes on the Sun and in the heliospherereveal themselves in the particle distribution insidethe magnetosphere. Omitting the internal magneto-sphere processes like plasma instabilities and waveactivities, which are currently not predictable, MHDor hybrid models of solar wind - magnetosphere cou-pling are at present the prevailing means to providespace weather related forecasting of the magneto-spheric particle fluxes for operational purposes. • Magnetospheric magnetic field variations determinethe particle dynamics, and disturbances in this fieldcaused by solar wind variations can drastically changethe near-Earth’s particle environment. • GCRs and SEPs penetrate deep into the Earth mag-netosphere. The resulting particle population de-pends on the rigidities of the primary particles aswell as on the magnetospheric magnetic field struc-ture and dynamics. • Enhancements of trapped electrons accelerated byinner magnetospheric processes are usually the con-sequence of interplanetary shocks, CME or high-speedstreams arrivals. • Low-energy particle precipitations in auroral regionsare usually manifestations of magnetospheric pro-cesses taking place during geomagnetic disturbances.It is essential for satellite operators to know the past,current and future condition of the space environment(particles and fields) around their own satellite, especiallyin case of actual satellite anomaly or before critical oper-ation periods. Measurements and modeling of high andlow energy particle fluxes, and observational data assim-ilation are of key importance for operative space weatherpredictions in near-Earth space.
Goal MEP-1: Description of the magnetospheric state
In order to move the predictability of particle fluxes for-ward, we first need a complete science based descriptionof the magnetospheric particle populations, which give riseto space weather effects (1st and 2nd priorities in PathwayII recommendations for maintaining existing capabilities).Solar wind conditions are the controlling factors for thenear Earth energetic particle population, but the previousstate of the system is also critical. The details of the re-sulting population always depend on the present driving condition and the prehistory of the event (timescales to beconsidered are of the order of several days to a week).Trapped energetic particles in the inner magnetosphereform the radiation belts. The inner proton belt is rel-atively stable, but the outer radiation belt comprises ahighly variable population of relativistic electrons. Solarwind changes produce changes to trapped particle trans-port, acceleration, and losses. Current understanding ofthe ways in which the magnetosphere responds to solar in-puts, indicate that the effectiveness of the input is highlydependent on the initial state. For example, magneto-spheric reconnection rates are believed to be dependenton the oxygen content of the tail in the reconnection re-gion, so that substorm triggering may be modified duringstorm time, when oxygen concentrations may be greatly el-evated. Moreover, the production of relativistic electrons,is believed to depend on a seed population of high energyelectrons as a result of earlier substorm activity. There arenumerous other examples for such preconditioning.Storm-time magnetospheric convection intensification,local particle acceleration due to substorm activity and res-onant wave-particle interaction are the main fundamentalprocesses that cause particle fluxes energization and loss.However, the details of the mechanisms that may be ableto contribute to these processes remain a subject for activeresearch. While progress has been made in the theoreti-cal understanding of these competing processes, there is asyet no clear consensus on which of these will be significantin particular situations, and no real predictive methodswhich can give precise fluxes at different local and univer-sal times. There is therefore a pressing need to confronttheoretical models with detailed measurements, in orderto resolve these shortfalls.Finally, there are short-term populations of ring cur-rent particles produced by substorms and enhanced con-vection. Currently our understanding of substorm onset isevolving rapidly, in particular with respect to local dipolar-ization structures. However, we are still a long way from anability to predict precise events, and a new physics under-standing is almost certainly required. Current spacecraftmeasurement configurations are probably not sufficient tomake accurate predictions. Since these effects are the ma-jor contributor to spacecraft failures due to charging, itis essential that current investigations are maintained andextended.
Goal MEP-1a Magnetic field and solar wind descrip-tion: • REQUIRE: MAINTAIN current continuous solar andsolar-wind observations as a basis for the predictionof magnetospheric disturbances (1st, 2nd, and 3rdpriorities in Pathway I for maintaining existing ca-pabilities). • REQUIRE: Advanced magnetospheric modeling isneeded to take into account local plasma processesaffecting the magnetic field variations producing par-48icle accelerations, losses etc. (4th priority in Path-way I for modeling). • REQUIRE: In order to provide the diverse systemlevel data set essential for evolving predictive mod-els of energetic particles, and to provide nowcastingof energetic particle fluxes, a required space weatherproduct, we should MAINTAIN similar space andground-based infrastructure as required for the pre-diction of GMD and GIC (see above) – Simultaneous GEO, LEO, MEO, GTO near real-time magnetic field and particle data collectionand processing. (1st and 2nd priorities in Path-way II for maintaining existing capabilities) – Measurements of current solar wind conditionsand solar UV monitoring for solar wind predic-tion. – Monitor magnetospheric activity and dynamicsby means of networks of ground based magne-tometers, radars and auroral imagers, includingspace born global auroral imagery. (6th priorityin Pathway I for maintaining existing capabili-ties). • REQUIRE: Improved magnetic field models (empir-ical, numerical) with particle tracing codes to form abasis for nowcast/forecast particle distributions, (1stpriority in Pathway II for maintaining existing capa-bilities). • REQUIRE: Improved models for solar wind propa-gation from the Sun. (1st, 2nd, and 3rd priorities inPathway I for modeling). • DESIRE: Accurate Magnetic field models to predictDst and forecast particle distributions. We suggestthis as a particularly fruitful area for modeling. • DESIRE: Visualization tools for magnetic fields andlow and high-energy particle distribution in geospace.
Goal MEP-2a: Specify extreme condition of soft parti-cle (keV) environment in Geospace - Surface charging
Dynamical variations of keV plasma, such as substorminjection, auroral particle precipitation, and field-alignedcurrents are a critical factor in surface charging of satel-lites at LEO and GEO. Thus soft plasma descriptions arean essential precursor for the mitigation of surface charg-ing problems from extreme conditions in the soft particle(keV) environment; this information is essential for satel-lite design. • REQUIRE: Monitoring soft particle fluxes by LEOsatellites (e.g., DMSP, POES) (1st Priority in Path-way II recommendations for maintaining existing ca-pabilities; 5th priority in Pathway I recommenda-tions for maintaining existing essential capabilities) • DESIRE: permanent auroral oval monitoring fromspacecraft in UV (like Polar) (7th priority in Path-way I recommendations for new instruments) • REQUIRE: Large databases of current and historicaldata obtained from in-situ particle measurements on-board spacecraft should be preserved (and compiledwith cross-calibration) as we need to analyze theoccurrence frequency distribution of extreme con-ditions of soft particles; Understanding the physi-cal mechanism of particle injection and precipitationand relating solar wind conditions with extremes inthe geospace environment is an important aspect inorder to make progress in predicting extreme condi-tions in the soft particle environment (1st priority inthe Pathway II recommendations for modeling).
Goal MEP-2b: Nowcast and forecast of soft particle(keV) environment in Geospace - surface charging.
The soft particle environment in geospace is dynami-cally changing depending on solar wind conditions. Under-standing the current and future soft particle environment(spatial distribution, time variation, energy spectra, etc.)is important to assess the risk of space assets and to exam-ine on-going satellite anomalies in geospace (1st priority inthe Pathway II recommendation for maintaining existingcapabilities; 1st priority in the Pathway II recommenda-tion for new instrumentation). • DESIRE: Ability to reconstruct three dimensionalparticle distributions using limited numbers of satel-lite observations based on the data assimilation methodwith magnetospheric models. • DESIRE: IMPROVE our understanding of the re-lationship between the solar wind parameters andthe variations of injecting/precipitating soft particlesfor correct predicting the space environment aroundGEO (2nd priority in Pathway II recommendationsfor modeling). Development of soft particle modelin geospace including supply and loss of soft particlevariations are important for the prediction.
Goal MEP-3a: Magnetospheric energetic particle mea-surements.
Trapped energetic electrons ( ∼ MeV) can penetrate space-craft shielding leaving their energy and charge embeddedin devices. This energy deposit contributes to total ioniz-ing dose and deep dielectric charging; the deposited chargecan build up leading to electrostatic discharge when abreakdown voltage is reached. Dose and damage lead tocatastrophic failure or progressive degradation of the per-formance of solid-state devices, including electronic com-ponents, solar cells, and focal planes. Electrostatic dis-charge can physically damage spacecraft materials, createshort circuits, or manifest itself as phantom commandsthrough electromagnetic or radio frequency interference.49rapped energetic protons and heavier nuclei (keV to GeV)cause dose and single event effects (SEE). This is especiallyimportant near the SAA.At the onset of most geomagnetic storms the outerzone of the radiation belts may be depleted in severalhours. Subsequently, the outer zone will some times buildup to levels higher than before the magnetospheric activ-ity began. A variety of processes can apply in differentconditions (see MEP1), with more extreme events sometimes causing prompt effects. There is no clear correla-tion between ring current enhancement, as measured byDst, and the effects in terms of relativistic electron pen-etration deeper into the outer zone, slot, and even innerzone. In the past it was believed that the higher the solarwind speed, the more likely is the event to lead to elevatedpost-event electron fluxes; however this has recently beencalled into question. Monitoring such events at GEO isroutinely undertaken. Given the very limited understand-ing currently available of the relative geoeffectiveness ofvarious solar wind disturbances (see above), the best prac-tice consensus is that excellent monitoring of the real timeenvironment (nowcasting) is the most useful product thatcan be provided to satellite operators. This, and well char-acterized descriptions of historical events, can be used tointerpret failures and improve the resilience of spacecraftdesign. • We REQUIRE high quality measurements of the en-ergetic particle environment in Geospace, particu-larly LEO and GEO. We need to MAINTAIN theexisting GOES satellite measurement, and ENSUREcontinued access to LANL GEO data, even if not inreal time. We NEED better energy resolution atGEO. • REQUIRE: maintain (and enhance) the availabil-ity of high-energy, widely distributed, multiple localtime, GEO energetic particle data (5th priority inPathway I recommendations for maintaining exist-ing capabilities; 1st priority in Pathway II for main-taining existing capabilities): • REQUIRE: We need to preserve access to data sets,current and historical, ground and space based (e.g.,preservation of LANL, Ground magnetometers, HFradars), in standard archival formats, in order to en-able detailed validation of physics models (1st prior-ity in Pathway II for archival research). • REQUIRE We need a standardization of instrumentdocumentation and documentation on data process-ing; a minimum level of documentation required foruser community should be identified. (General rec-ommendation for Teaming, point g) • REQUIRE: Need to establish methodologies and met-rics for validation and calibration models and of data.(General recommendation for Teaming, point g) • DESIRE: hosted radiation monitor payloads at leastat LEO and L1, Perhaps in the long run widespreadminiaturised radiation monitors can populate all otherkey regions of geospace from field aligned accelera-tion regions to the ring current and magnetotail. • REQUIRE: To improve our understanding of pro-cesses leading to better understanding of the radia-tion belt dynamics, we need continuing support ofthe Van Allen Probes (RBSP) or a similar mission(2nd priority in Pathway II for maintaining existingcapabilities).
Goal MEP-4: Model of magnetospheric particle accel-eration.
It is essential for satellite operators to know if rela-tivistic electrons can be expected to show a major in-crease. Thus processes of acceleration, transport, and lossof energetic electrons should be the basis for predictingthe dynamics of trapped energetic particles. However, asremarked previously, understanding geoeffectiveness is amajor shortfall in current theoretical understanding. Cur-rently understanding of Energetic Electron and Proton ac-celeration mechanisms is insufficient to discriminate be-tween the effectiveness of different energization, transportand loss processes at different L-shells and local times.Quantitative assessment of the predictive properties of cur-rent and emerging models is thus essential. Hence detailedtesting against fine-grained observations is needed. • REQUIRE: We need to preserve access to data sets,current and historical, ground and space based (e.g.,preservation of LANL and ground-based magnetome-ters), in standard archival formats, in order to enabledetailed validation of physics models. In the futurecubesats should be used in detailed campaigns forthis purpose also (1st priority in Pathway II for ar-chival research). • REQUIRE: Need to establish methodologies and met-rics for validation and calibration models and of data(General recommendation for Teaming, point g). Wesuggest the establishment of an energetic particle in-dex for MEO high-energy flux. Multipoint in-situmeasurements from MEO satellites can provide theneeded information about trapped particle popula-tion.The end goal should be a fully predictive dynamicalmodel of radiation belt particle populations, at differenttimes, L-shells and local times, related to geomagnetic ac-tivity indices (especially Dst) and solar wind conditions(velocity, field orientation and pressure). Such a modelwill certainly also need to encompass an accurate descrip-tion both of the current conditioning of the system and thecurrent and predicted inputs. It should be capable of pre-dicting extreme events with an accuracy that increases asthe event realistic approaches, until realistic warnings can50e given of major disruptions. Moreover, such a model (ormodels) will have provided a realistic basis for improvedengineering designs and procedures that mitigate potentialimpacts.
Goal MEP-5: Description of SEP and GCR penetra-tion into the magnetosphere.
SEP and GCR originate from solar system or the Galaxy,respectively, and propagate to the Earth’s orbit. Energeticparticle can cause dose and SEE either through direct ion-ization events, or through the nuclear showers they create.The terrestrial magnetic field topology in general effectsthe penetration of these particles into the near Earth en-vironment. While GCR particles of specific energies canenter the Earth’s magnetic field, solar particles of rela-tively low energies cannot penetrate deep into the Earth’smagnetosphere. Magnetospheric structure changes duringgeomagnetic disturbances can provide expansion of the re-gion populated by energetic particles coming from helio-sphere. Knowledge of the geomagnetic cutoff is thus im-portant for satellite and aviation operators, as it controlsparticle fluxes at low altitudes. The latitude of the pene-tration region for particles of higher energies depends ontheir rigidity and the geomagnetic activity level. On occa-sion SEP penetrate deep into the atmosphere where theyproduce the secondary particles measured by neutron mon-itors. Independent on-ground measurements give impor-tant information on SEP spectra, while SEP variations arealso observed by satellites in GEO and LEO. The slowly-varying GCR component is a persistent threat, while SEPare the main source of variable radiation effects on com-mercial aircraft, particularly at high latitudes, and rep-resent a critical hazard to astronauts, as well as havingeffects on spacecraft.Energetic particles originating from SEP and GCR cancause dose and damage in similar ways to trapped elec-trons, but also cause SEE. We need observations and mod-els to tackle these factors (3rd priority in Pathway III formaintaining existing capabilities). SEP forecasting basedon solar observations is of key importance. This opportu-nity is described in detail in the SH sections. • MAINTAIN energetic particle monitoring to specifysolar particle access at different latitudes (1st and2nd priorities in Pathway II for maintaining existingcapabilities). • MAINTAIN measurements onboard polar LEO: POES,MetOP, Meteor M, in proton channels 10 MeV andabove. (5th priority in Pathway I for maintainingexisting capabilities). • MAINTAIN supplemented monitoring at L1 (ACE)and GEO (GOES, LANL, Electro-L) to establish freespace flux. • MAINTAIN solar observations in UV (See SH sec-tion). • REQUIRE: IMPROVE models of the effective ver-tical cut-off rigidities dependent on local (or univer-sal) time, and geodetic coordinates (altitude, lati-tude and longitude), as well as on the conditions ofgeomagnetic disturbances described by the Kp/Dst-indices, and possibly also auroral electrojet indices,AE/AU/AL which can potentially modify access.
Appendix E.3. Ionospheric variability
The users of ionospheric space weather services havedifferential needs depending on the application areas. GNSSusers in precise and safety of life applications need now-casts and short-term forecasts of disturbed periods, so thatthey are aware of potential for disruption of GNSS signals,leading to higher uncertainties in measurements, and insevere cases, to loss of service. In surveying, forecasts onelectron density variations up to 1-2 days and nowcasts and1-day forecasts on scintillation would be desirable for plan-ning purposes. For aviation aircraft and ground-systemssupporting them we need both short-term alerts and fore-casts of disturbed conditions with 0.5-1 day lead times(e.g., at least six hours before take-off) in order to be pre-pared for potential disruptions in satcom and HF signals.Operators of space radars require nowcasts and short-termforecasts of TEC in order to correct for range and bearingerrors in radar tracking of space objects in LEO.We note that statistical ionosphere models tuned withdata from ground-based networks or LEO satellites can inmany cases provide relatively good results for nowcasts orshort-term forecasts in regional or global scales. However,with increasing lead times more comprehensive physics-based modeling with data assimilation is required.
Goal IO-1: Understand/quantify the benefits of dataassimilation in ionospheric modeling.
In the work to get longer lead times in predictionswith adequate reliability space weather research can ben-efit from synergies with meteorology (c.f. General recom-mendations for Collaboration between agencies and com-munities, point m). Data assimilation is today the stan-dard approach in numerical weather prediction. In spaceweather assimilation is utilized in some research projects,but comprehensive understanding on how assimilation couldin optimal way support ionospheric SWx forecasts is stillmissing.
Goal IO-1a: Upgrading MLTI models with assimilationcapability
Variability in the ionospheric electron density is con-trolled by several processes that are coupled with solaractivity, and with the Earth’s magnetosphere and neutralatmosphere (thermosphere). In thermosphere global circu-lation patterns, thermal conditions and chemistry all havetheir impact to the evolution of ionospheric conditions.Therefore, priority in the upgrading work should be givento such models that have the capability to take into ac-count the various coupling processes.We recommend the following:51
REQUIRE, IMPROVE/NEW: Advance projects inwhich the research community can investigate theopportunity to use research models for Magnetosphere-Lower Thermosphere-Ionosphere-(MLTI) system inextensive use with assimilation capability (4th pri-ority in Pathway I recommendations for modeling).The CCMC service maintained by NASA is an ex-ample of a platform that could be upgraded to be-come a forum for centralized assimilation code de-velopment as a joint community effort. Especiallyin the development phases, solutions should be fa-vored and further developed that have flexible inter-faces for adopting several types of observations, e.g.,solar (spectral) irradiance, ionospheric plasma con-vection, 2D and 3D views of electron density, andneutral wind properties (chemical composition, den-sity, temperature, wind).
Goal IO-1b: Defining optimal observation capabilitiesfor ionospheric SWx services.
For the mission to utilize both observations and mod-els in ionospheric SWx forecasts it will be valuable toknow which instruments provide the best support for im-proved model results. The optimal use of data requiresimproving/developing actual/new measurement and mod-eling techniques taking into account current and futurecustomer requirements. In particular, the development ofdata-driven, physics-based models and associated assimi-lation techniques must be supported by funding agencies.Furthermore, it has to be investigated which temporal andwhich spatial resolution is needed to provide the optimumcost-benefit ratio in operational use. Dedicated researchprojects are needed to answer these questions.We recommend the following: • REQUIRE, IMPROVE/NEW: During the comingfive years national funding agencies, space agencies,EU and other stake holders should support researchprojects which investigate the observational needsfor advanced ionospheric space weather modeling andforecasts in relation to existing and planned groundand space based monitoring capabilities. Fundedprojects should include sensitivity analyses that showhow much different measurements with variable timeand space resolutions contribute to improving ourability to forecast. Potentially new metrics need tobe developed in order to quantify in an objective waythe benefits from various input data sets (Generalrecommendations for Teaming, point g). The stud-ies should demonstrate how a complementary mix ofmeasurements can be used effectively in operationalforecast systems. Suggestions of optimal cost-benefitsolutions should be one outcome from these researchprojects. • REQUIRE, MAINTAIN/IMPROVE: To support thework described above the research groups and agen- cies maintaining SW instrumentation should estab-lish test beds for evaluating new observation meth-ods, techniques and data products and for perfor-mance validation of ionospheric forecast codes at high,middle and low latitudes (General recommendationfor Teaming, point f). Such test beds can be identi-fied from the existing ground and space based iono-spheric monitoring capabilities, many of which canprovide long data records from versatile instrumen-tation. Considering ground based measurement fa-cilities only, a test bed area should be covered by adense network of GNSS receivers accompanied by awide variety of other relevant instrumentation (iono-sondes, ISR radar, magnetometers, riometers, HF-radars, Beacon receivers). Preference should be givento such set-ups that can provide also neutral atmo-spheric measurements (wind, density and tempera-ture, in particular at low and mid-latitudes) and aresupported frequently with relevant space-based ob-servations. Suitable, already existing candidates fortest-bed areas are often located in the surroundingsof ISR systems. For example, the measurements ofthe Resolute Bay and Poker Flat ISRs in northernUS and Canada, of the EISCAT ISRs in Fennoscan-dia and Svalbard, of the Millstone Hill ISR in USMassachusetts and of the Jicamarca radar in Peruare supported by networks of relevant instrumenta-tion. • DESIRE, MAINTAIN/IMPROVE: Science organi-zations involved in SW (e.g., COSPAR, ILWS, WMO,ISES) should do overarching coordination and reviewwork in order to compose unified view from the stud-ies described above (i.e., re-do the Roadmap taskthat is presented here, but with the input from thevarious sensitivity studies; see General recommenda-tions for collaboration between agencies and commu-nities). Recommendations from this work should i)help in identifying from existing assets those whichdeserve prioritization in maintenance ii) and sup-port the planning work for future investments in SWinstrumentation both in national and internationallevel.
Goal IO-2: Improved understanding on physics of iono-spheric processes disturbing trans-ionospheric radio wavepropagation.
In ionospheric research there are still several topics thatare relevant for SWx prediction but are lacking for generalconsensus on the underlying physics. Examples of suchtopics are processes associated with radio scintillation (inparticular plasma turbulence at high latitudes and bubbleformation at equatorial latitudes) and the coupling be-tween neutral atmospheric dynamics (wind and waves) andionospheric disturbances. Systematics in the appearanceof ionospheric storms in different latitudes, local times andduring the different storm phases has not been studied52omprehensively yet, which complicates the efforts evenfor short-time global forecasts.
Goal IO-2a: Conducting ionospheric research with en-hanced observations.
The spatial resolution of measurement stations provid-ing ionospheric data has great variability. Some regionsare populated with dense GNSS receiver networks whileno ground-based receivers are available in the ocean ar-eas. To fill this gap that is typically for ground basedmeasurements, space based monitoring techniques such asradio occultation, and satellite altimetry data can be used.While ionospheric plasma can be probed with a wide vari-ety of different cost effective and robust instrumentation,monitoring of thermospheric properties (chemical compo-sition, neutral wind, density and temperature) is challeng-ing. Achieving reliable continuous estimates of the globalmagnetospheric energy input as Joule heating or as ener-getic particle precipitation is also difficult.We recommend the following • REQUIRE: Advance combined use of ground-based,space based and airborne instrumentation in iono-spheric modeling and forecasts (6th recommendationin Pathway I for maintaining existing capabilities;2nd recommendation in Pathway III for new instru-mentation). The already existing ground-based net-works (magnetometers, ionosondes, riometers, HF-radars, Beacon and GNSS receivers) should be main-tained and their data dissemination systems shouldbe homogenized and streamlined. Solar SSI mea-surements, Beacon transmitters, Radio occultationreceivers and altimeter radars on-board LEO satel-lites are examples of data sources which can com-plement the specific view of ground-based measure-ments to jointly lead to a comprehensive image ofthe physical processes. Efforts for open data pol-icy should be supported (MAINTAIN/IMPROVE,MAINTAIN refers to the existing instrumentation,IMPROVE refers to measurement in ocean areas andto upgrades in data dissemination and to open datapolicy, c.f. General recommendations for collabora-tion between agencies and communities, point i). Inparticular, efforts to get access for science commu-nity to the data archives of Real Time Kinematic(RTK) positioning networks should be supported.Commercial enterprises in several countries maintainRTK systems (dense GNSS receiver networks) thatcan provide information on ionospheric electron con-tent with much better time and space resolution thantypically available in scientific missions. • REQUIRE, IMPROVE/NEW: Establish and main-tain collaboration with research groups and agencieswhich conduct thermospheric and magnetosphericresearch in order to search new ways to get neu-tral atmospheric or Joule heating data as input forionospheric model testing and forecasts. Advance- ments in Fabry-Perot interferometry should be har-vested, especially where advanced instrument tech-nologies will open up daytime observations. Oppor-tunities provided by some forthcoming satellite mis-sions should also be investigated (e.g., the NASAmissions ICON and GOLD for thermospheric mea-surements, the US-Taiwanese atmosphere-ionospheremission COSMIC II and the ESA mission Swarm forMLTI research). • DESIRE: Advance the search of new data sources tosupport SWx forecasts. Examples of new potentialsources are GNSS reflectometry, SAR imaging, andmulti-satellite radio occultation sounding by COS-MIC II satellites.
Goal IO-2b: Enhancing system level modeling of theionosphere.
Models available today provide a mosaic on processesfrom different parts of the system (with separate piecesfor high latitudes and low latitudes, for magnetosphere-ionosphere coupling and ionosphere-thermosphere coupling,for global processes and micro-scale processes etc.) butknowledge on the linkage between the different pieces ismissing. Today ionospheric models are typically coupledwith neutral atmosphere models (e.g., MSIS) that describethe climatology quite well, but they fail to describe theprocesses in lower atmosphere which affect ionospheric con-ditions (tides, gravity waves, planetary waves). For thisreason, the models are not able to reproduce properly e.g.,the background and seeding conditions for bubble forma-tion. It is important to have a model where ionosphere isproperly coupled with such neutral atmosphere and mag-netosphere models that are capable to describe properlyat least those processes that control ionospheric electroncontent.We recommend the following: • REQUIRE, IMPROVE/NEW: Advance efforts forthree-dimensional imaging and modeling of ionosphericphenomena with the goal to gain better understand-ing on non-equilibrium plasma processes and on causeand consequence relationships between processes indifferent scale sizes (particularly between regionaland microscales in order to gain better understand-ing on processes causing scintillation). • DESIRE, NEW: Advance efforts for the developmentof a framework where the whole atmosphere (up to ∼
400 km altitudes )is treated as one system. Thatshould give a better means to understand verticalcoupling, and also stimulate stronger links betweensolar-terrestrial research community and the meteo-rological community.53 ppendix F. Concepts for highest-priority instru-mentation
Appendix F.1. Binocular vision for the corona to quantifyincoming CMEsRationale:
Knowledge of the magnetic structure of thesolar wind, and in particular that of coronal mass ejec-tions, that will interact with the magnetospheric field thatin turn drives the underlying ITM is needed at least aday prior to reaching geospace, i.e., well before reachingthe solar-wind sentinel(s) positioned a million miles (orabout an hour of wind travel time) upstream of Earth atthe Sun-Earth L1 point. This knowledge, in particular ofthe magnetic direction and strength of the leading edge ofcoronal mass ejections [CME]s) can be obtained by forwardmodeling an observed solar eruption through the embed-ding corona and inner heliosphere, provided the magneticstructure of the erupting structure is known. Derivingthe magnetic configuration of an erupting solar active re-gion based on surface (vector-) field measurements aloneyields ambiguous results at best; these are insufficient forthe purpose of MHD modeling of CMEs. New field mod-eling methods have been developed that can utilize thecoronal loop geometry to constrain the model field, par-ticularly when 3D information on the corona is available(e.g., Malanushenko et al., 2014). Binocular imaging ofthe active-region corona at moderate spatio-temporal res-olution enables the 3D mapping of the solar active-regionfield structure prior to, and subsequent to, CMEs, therebyproviding information on the erupted flux-rope structure.Combined with full-disk coronal imaging and - if feasiblewithin the mission parameters - with coronagraphic imag-ing provides valuable information on the direction taken bythe nascent CME en route to the inner heliosphere throughthe high corona.
Objectives:
Obtain EUV images of solar active regions,of the solar global corona, and (if not provided by otherinstrumentation) of the inner heliosphere from a perspec-tive off the Sun-Earth line, to complement EUV imagesfrom existing instruments on the Sun-Earth line such asSDO/AIA or, if not available, by a second identically-equipped spacecraft.
Key requirements:
EUV images of active regions at(at least) two wavelengths (characteristic of 1-2MK and2-3MK plasma) at ∼ ∼ Implementation concept:
A single two-channel full-diskEUV imager a 1 arcsec resolution with on-board data pro-cessing to (selected) high-resolution active region imagesand binned full-coronal images (to reduce overall teleme-try rates). A compact coronagraph if needed. In a slightlyelliptical solar-centric (“horseshoe”) orbit drifting away from Earth at a rate of no more than about two degreesper year for the first three years after reaching 5-degreesof separation from the Sun-Earth line. If combined withSDO/AIA a single spacecraft suffices; if a standalone mis-sion, two similar spacecraft are needed to drift apart bythe required separation for a period of at least one year.Each spacecraft could be scoped within, e.g., the NASASMall EXplorer (SMEX) envelope.
Status:
Proposed in this Roadmap. Whereas the STE-REO mission has given us a temporary glimpse of stereo-scopic coronal EUV imaging, the field modeling capabili-ties at the time did not yet exist and the image resolutionwas insufficient on the STEREO and SoHO spacecraft.
Supporting observations:
New observational technolo-gies can support the goals of determining the 3D structureof the magnetic field in source regions of solar activity,particularly when combined with the above direct obser-vations and modeling techniques. This includes radio ob-servations such as, for example, with proposed instrumen-tation for FASR, etc., particularly when multi-frequencyultra-wideband radio array(s) are available over frequencyrange of 50 MHz to 20 GHz, with full Sun images at allwavelengths taken once per second (partly completed inChina, US development efforts continuing).
Appendix F.2. 3D mapping of solar field involved in erup-tionsRationale:
A key science goal in this roadmap is to de-termine the origins of the Sun’s activity to help predictvariations in the space environment. Knowing the low-lying twisted filament-like field configurations and theirembedding field in the deep interiors of unstable active re-gions before and after eruptions is key to determining whatpropagates towards Earth to drive space weather, which,in turn, is needed to forecast the dynamics and coupling ofthe Earth’s magnetosphere-ionosphere-atmosphere systemdriven by the incoming CMEs. Magnetic stresses involvedin coronal mass ejections cannot be observed directly, butrequire modeling based on observations of the vector mag-netic field at and above the solar surface, guided by, andcompared to, observations of the solar atmosphere in whichstructures from chromospheric to coronal temperatures arecarriers of the electrical currents that reflect the system’sfree energy converted to power eruptions. In the contextof Pathway 1, the primary goal is to observe electricalcurrents threading the solar surface, and observing the de-tails of the low-lying configurations known as filaments andtheir embedding flux ropes before, during, and after erup-tions to quantify the 3D field ejected into the heliosphere.In the context of Pathway 3, the same instrumentationprovides observations of the small-scale processes involvedin the triggering of flares and eruptions, needed for short-term SEP forecasts, and for CMEs forecasts of more than2-4 days and SEP all-clear forecasts in the coming hours.
Objectives:
Obtain vector-magnetic measurements ofactive regions at the solar surface and within the chro-mosphere to measure electrical currents. Image the solar54tmosphere from 10,000K up to at least 3MK at matchingresolutions to observe all field structures that may carryelectrical currents. Provide observations before, during,and after eruptions to derive CME field structure to driveheliospheric models, to study how the nascent CME is re-structured as it propagates through the active-region mag-netic field.
Key requirements:
High-resolution imaging (at match-ing resolutions of 0.2 arcsec or better) is needed through-out active-region atmospheres, spanning the entire activeregion footprint, with observations at temperatures char-acteristic of photosphere, chromosphere, and corona. Spectro-polarimetric observations for photospheric and chromo-spheric magnetic field measurements. Imaging cadence ofapproximately 10 seconds, or better. (Near-)Continuoussolar viewing.
Implementation concept:
Geo-synchronous or low-Earthorbiter in high-inclination orbit with UV-optical telescopewith polarimetric imaging capabilities, enabling photosphericand chromospheric imaging and polarimetry. Soft X-rayand EUV imagers. Substantial ground-based network toenable large effective telemetry rates, and/or onboard im-age selection from large memory.
Status:
Considered as a multi-agency mission betweenJAXA, ESA, and NASA to share cost and expertise, insupport of international space-weather research.
Appendix F.3. Strong GICs driven by rapid reconfigura-tions of the magnetotailRationale:
The processes of energy input from the so-lar wind and storage in the magnetotail are now reason-ably well-understood, with further recent discoveries fromthe THEMIS and Cluster missions beginning to reveal thetantalizing physics of the development and penetration ofEarthward propagating bursty bulk flows and localizeddipolarizing flux tubes which transport flux and plasmaEarthwards. However, the nearer Earth dynamics whichcouple these flows to the inner edge of the plasmasheetand how exactly the flow braking region couples to theionosphere and produces large field-aligned currents andhence GICs are poorly understood. A two-constellationsatellite mission architecture is proposed. The first willreveal the key plasma physical processes associated withplasma instabilities and flow braking at the inner edge ofthe plasmasheet, in the transition region from dipolar totail-like magnetic fields; the second will reveal the natureof magnetosphere-ionosphere (M-I) coupling in the auro-ral acceleration region on field lines conjugate to the inneredge of the plasma sheet. From the GIC perspective, theprocesses that control the rate of energy transport and theactual partition between competing routes of dissipation inthe coupled M-I system remain insufficiently understood.In terms of space weather impacts, the conditions lead-ing to and the physical processes responsible for enablinglarge field aligned currents to reach the ionosphere anddrive large GICs are not known.
Objective:
Determine the M-I processes controlling thedestabilisation of the near-Earth magnetotail, which willlead to the establishment of large field-aligned currentsresulting in extreme GICs.
Key requirements:
To meet this objective we need theflight of two coordinated satellite constellations in the in-ner edge of the plasmasheet, which marks the transitionregion between tail-like and dipole fields, and on the conju-gate auroral field lines below. It should be noted that thechallenge of these constellation missions lies in the popula-tion of magnetospheric key regions and not in particularlyfancy or expensive instrumentation.
Transition Region Explorers:
Three-dimensionalplasma and electrodynamic fields (E (at least AC) and B)in the transition region between dipole-like and tail-likefields, which is the originator for large field-aligned cur-rents. Coverage is required from close to geosynchronousorbit to around 10-12 Re. This could be accomplished byat least one classical well-instrumented spinning spacecraftwith magnetic field, electric field, plasma measurementsfor pitch angle resolved electrons and ions in the energyrange from around 10’s eV (as low as possible withoutASPOC) to several hundred keV, including species reso-lution. This likely requires a standard suite of particleinstruments including an electrostatic analyser, solid statedetector, and ion composition spectrometer. Potentiallythis satellite should carry sufficient fuel to change apogeealtitude between 8-12 R E during the course of the mission.This should be supplemented by a swarm of around 4smaller spacecraft approximately 1 R E from the mother,providing coverage in the azimuthal and radial directions.The smaller daughters could carry a more limited basicplasma payload of a magnetometer, miniaturised electro-static analyser, and Langmuir probes for total (includingcold) plasma density and temperature. Field-Aligned Current Explorers:
Multi-pointplasma and electrodynamic fields in the auroral accelera-tion region in order to determine the dynamical couplingbetween the magnetosphere and the ionosphere includingthe partitioning and exchange of energy between currents,waves and particles which are believed to act as a gate forthe ability of the tail to drive FAC through to closure andeventual energy dissipation in the ionosphere. Operationalaltitudes should encompass the range of around 4000 kmto 1 Re, utilising conjugate measurements from differentaltitudes on the same field line, and multiple along tracksatellites providing a capability to resolve spatio-temporalambiguity related to the filamentary nature of FAC and ex-amine and distinguish between the dynamics of Alfv´enicand inverted-V auroral acceleration processes. Optionallyan additional single 3-axis stabilized satellite for in-situauroral imaging.Baseline of two or three spinning spacecraft providingelectric (via wire booms) and magnetic fields and wavesmonitoring, as well as plasma electrons and ions from ener-gies of around 10 eV to 30 keV, likely from an electrostaticanalyzer. Options to add higher energy coverage from an55olid state detector, to resolve the populations up to some50 keV should also be studied. Again, Langmuir probeswould provide significant information about very low en-ergy populations below the energy range of the particleinstrument. Payload for the 3-axis stabilized satellite forin-situ auroral imaging is TBD.
Auroral Imaging and Supporting Ground Net-works and LEO Satellite Constellations:
The con-stellation missions should be complemented by conjugateauroral imaging from the ground, as well as supportingnetworks of ground-based magnetometers, HF radars, ri-ometers etc, to aid the identification of the onset locationand the resolution of the spatio-temporal ambiguity of theprocesses leading to large dB/dt. Existing or newly pro-vided constellations of low-Earth orbiting satellites whichcan additionally monitor the precipitating electrons as ameasure of ionospheric conductivity changes will providevaluable complementary measurements; global measure-ments of the background large scale FAC distributions,such as available from AMPERE, provide the capabilityto identify onset locations with respect to the nightsideconvection pattern.
Incoming Tail Flows and Upstream Solar WindMonitor:
Measurements of incoming flows in the centralplasmasheet of the more distant tail are also required toassess incoming flows in the same meridian. These couldbe potentially be provided by pre-existing assets, such asGeotail, Cluster, THEMIS, or perhaps MMS in an ex-tended mission phase. An upstream solar wind monitoris of course required as always
Implementation concept:
The challenge for mission im-plementation is not in the instrumentation, which is read-ily available and should thus not be a cost driver. Rather,the challenge lies in the positioning of a sufficient numberof spacecraft at the two key locations in space, and thusin both the possible orbit configuration and the numberof spacecraft. Likely this requires detailed future studyof at least the potential orbits which can launch and de-liver the satellites into the appropriate operative orbits atmodest cost. We recommend that the formulation of aninternational study with representatives of national spaceagencies is considered, perhaps in the context of ILWS.
Status:
Two satellite-constellation concept proposed inthis roadmap.
Supporting observations: by existing mid-tail and up-stream solar wind satellites, as well as existing complemen-tary multi-instrument ground-based networks and existingLEO satellite constellations.
Appendix F.4. Coordinated networks for geomagnetic andionospheric variabilityRationale:
Our understanding of space weather im-pacts on the upper atmosphere is crucially dependent onmeasurements from rich networks of ground-based instru-ments, including (a) magnetometers to observe how elec-tric currents in the ionosphere are modified by space weather, plus (b) a wide variety of radar and radio techniques tomonitor changes in the density, motion and temperaturesof ionospheric plasmas, as well as (c) optical techniquesto measure thermospheric winds and temperatures. Thesedata sources are all key inputs into the development ofimproved models of the atmosphere and its response tospace weather. This will become even more important infuture as we focus on assimilative approaches to modeling.As in meteorology, these approaches will advance our sci-ence (e.g., through use of reanalysis techniques to revealnew systematic features in the data) and will also providean efficient practical basis for future applications of ourscience. These assimilative approaches are significantlyenhanced by the availability of diverse datasets from spa-tially dense networks as these data then provide strongconstraints on the assimilation. We need to promote theseground-based networks as a global system for scientificprogress on space weather, so that each individual (andoften independently funded) instrument provider (and re-sponsible funding agency) sees how their contribution fitsinto the wider picture, i.e. that a local contribution buildsand sustains local access to a global system.
Objectives:
To make a step change in the internationalco-ordination, and delivery, of ground-based space weatherobserving systems to optimize our ability to observe spaceweather processes. This must include increased engage-ment with modelers, operators of space-based sensors, andother consumers of space weather data, in order to ensurethe optimum interaction between the collected data andstate-of-the-art international models, and the synthesis ofthese data and model results into operational tools whoseoutputs can be made available to the applications andtechnology community. This would be a major advance onthe current situation where ground-based instruments aremostly established and supported by individual nationalprograms, with only a few projects formally constitutedas multi-national programs (EISCAT being the notable ex-ample). There are a good number of projects that operateinternationally through working level agreements in thescientific community (e.g., SuperDARN) but experienceshows that these are difficult to sustain in modern condi-tions; they rather reflect an older (make-shift) way of work-ing that dates as far back as the IGY in 1957/58. Givenmodern approaches to funding and governance, these ob-serving systems need a more formal international structurethat can give them the continuous support and stimulusthat they need to deliver their full scientific potential fora future operative space weather system.
Key requirements:
Maintenance and extension of theSuperDARN network to measure electric fields in the high-and mid-latitude regions at least in the north hemisphere,preferably both (these measurements are a crucial factorin modeling the ionospheric, magnetospheric and radiationbelt response to space weather); high-resolution volumet-ric measurements of ionospheric properties by incoherentscatter radars (ISR) at several locations (to resolve thedetailed ion chemistry and plasma physics at work in the56onosphere); rich networks of magnetometers, GNSS re-ceivers, ionosondes and riometers to provide regional andglobal maps of key ionospheric properties including iono-spheric current systems (auroral, equator and Sq), totalelectron content and ionospheric scintillation, ionosphericcritical frequencies and layer heights and D region absorp-tion; improved operation of Fabry-Perot interferometers(FPI) to enable daytime as well as nighttime measure-ments of thermospheric temperature winds. It is highlyrecommended to ensure a concentration of networked in-struments, including FPI, around major facilities such asincoherent scatter radars, as these provide vital context forthat technique. These concentrations of instruments willallow us to use their locations as a scientific test bed wherewe can explore the detailed response of the ionosphere tospace weather.
Implementation concept:
Establish a global programat inter-agency level for coordination of space weather ob-serving systems, perhaps similar to coordination of spaceexploration activities. The involvement of agencies is cru-cial as it is vital to involve funding bodies to develop asustainable system that is subject to periodic review andwhere there is a proper emphasis on, and awareness of,the global nature of the program. The program wouldestablish working groups with strong expert membershipto carry out its technical tasks, including detailed reviewof measurement requirements, review of advances in in-strument technology, coordination with space-based mea-surements, recommendations on standards, exploitation ofsecondary data sources especially radio astronomy (muchof their “noise” is actually ionospheric signals that we wishto exploit), etc. The crucial aspect of this program is tobuild a framework where individual agencies can see thata modest contribution enables global science and, in par-ticular, is the logical way to enable first-class participationby the scientific community that they support.
Status:
Proposed in this Roadmap.
Appendix F.5. Mapping the global solar fieldRationale:
The global solar magnetic field extends outinto the heliosphere. It defines the structure of the helio-sphere, including the position of the heliospheric currentsheet and the regions of fast and slow solar wind, and playsa key role in space weather at Earth: (1) The interactionof CMEs with the ambient field impacts their geoeffective-ness. (2) The connection of the heliospheric magnetic fieldto CME-related shocks and impulsive solar flares deter-mines where solar energetic particles propagate. (3) Thepartitioning of the solar wind into fast and slow streams isresponsible for recurrent geomagnetic activity. The Sun’ssurface magnetic field is a vital ingredient to any predic-tive model of the global magnetic field, as it is used toderive boundary conditions. Global magnetic field mod-els (both the simpler potential-field source-surface (PFSS)models, and the more sophisticated MHD models) haveshown significant success in describing coronal and helio-spheric structure. These models typically use magnetic maps of the photospheric magnetic field built up over asolar rotation, available from a ground-based and space-based solar observatories. Two well-known problems arisefrom the use of these “synoptic” maps. First, the mapscontain data that is as much as 27 days old. The Sun’smagnetic flux is always evolving, and these changes in theflux affect coronal and heliospheric structure. Second, theline-of-sight (LOS) field at the Sun’s poles is poorly ob-served, and the polar fields in these maps are filled with avariety of interpolation/extrapolation techniques. Unfor-tunately, these observational gaps can strongly influencethe solution for the global magnetic field. In particular,poorly or unobserved active regions at the limbs (as viewedfrom Earth) as well as inaccurate polar field estimates canintroduce unacceptable errors in the field on the Earth-facing side of the Sun.
Objective:
Model the evolving global solar magneticfield. This requires the near simultaneous observation ofthe Sun’s magnetic field over a larger portion of the sun’ssurface than is available from the Earth view alone. Ob-taining photospheric magnetograms off of the Sun-Earthline off of the east limb (portion of the Sun with the old-est observations as viewed from Earth), to complementmagnetograms obtained along the Sun-Earth line by SDOand ground-based observatories, is the most crucial com-ponent. Obtaining magnetograms of the Sun’s polar fieldsover a few years is required to understand the evolution ofthe Sun’s polar magnetic flux.
Key requirements:
Ideally, several spacecraft would ob-serve the Sun’s magnetic field continuously, including thepolar fields, but such a plan is unlikely to be economicallyfeasible in the foreseeable future. The processes by whichthe magnetic flux on the Sun evolves have been studiedfor many years, and resulted in the construction of fluxtransport models capable of predicting the evolution of thefield. The incorporation of magnetograms away from theSun-Earth line would be used to augment existing, Earth-view magnetograms to capture a significantly larger por-tion of the Sun’s evolving flux. LOS magnetograms withMDI resolution and approximate cadence are likely to beadequate, although vector magnetograms with HMI reso-lution and cadence are desirable. Flux transport modelsalso predict the evolution of the Sun’s polar fields, but arelargely uncalibrated there. Observing polar flux evolutionwith MDI resolution over a few years would significantlyconstrain these models. EUV or X-ray imaging (STEREOcadence/resolution) to capture coronal holes and evolvingstructures for model validation from all of these views aredesirable.
Implementation concept:
Primary instrument: Full-disk magnetograph with MDI-like spatial resolution andhourly time resolution in an ecliptic orbiting spacecraftreaching at least 45 degrees off the Sun-Earth line. Orbitsgoing beyond this point are desirable. Given such a space-craft, a heliospheric imager would augment the goals of (1)and (4) by imaging earth-directed CMEs. If feasible, X-rayor EUV imaging (1 channel) at STEREO spatial resolu-57ion and cadence are desirable. A separate, high-latitude(30 degrees or more above the ecliptic) spacecraft missionof a few years with the same instrumentation is desirable.
Status:
Images from Solar Orbiter may be sufficient toprovide testing of concept of far side imaging, but are notadequate to fulfill the goal of more continuous monitor-ing of a larger portion of the Sun’s magnetic flux. SolarOrbiter may partially fulfill high latitude mission require-ments at the latter stage of the mission.
Supporting observations:
Direct imaging data of the so-lar atmosphere (such as possible with the STEREO space-craft) or indirect information derived from far-side helio-seismology (such as with SDO/HMI and GONG) provideuseful constraints, but are no substitute for direct magne-tography because these methods do not provide adequateinformation on the magnetic field.
Appendix F.6. Determination of the foundation of the he-liospheric fieldRationale:
The global solar magnetic field plays a cru-cial role in space weather at Earth. It influences the in-ternal magnetic structure of interplanetary coronal massejections; the connectivity of the magnetic field determineswhere solar energetic particles propagate, and structure ofthe field determines whether fast solar wind streams willcross the Earth’s location. An accurate representation ofthe time-evolving global solar coronal magnetic field is arequired input to models of prediction, eruption and prop-agation of CMEs through the solar wind.
Objectives:
Determine and obtain a critical set of multi-wavelength coronal magnetometric observables for constrain-ing the global magnetic field. Develop methods for incor-porating these observations into global MHD models of thesolar corona.
Key requirements:
Testbeds of synthetic polarimetricmeasurements at multiple wavelengths to provide diag-nostics related to the Zeeman and Hanle (saturated andunsaturated) effects and coronal seismology. Techniquesfor efficiently modifying global MHD models of the solarcorona to match data, synthetic or observed. Ultimately,full-sun synoptic observations sufficient to enable a data-assimilative, real-time updated representation of the globalcoronal magnetic field.
Implementation concept:
Different wavelengths diag-nose different aspects of the solar coronal magnetic field- strong vs. weak field, disk vs. limb, eruptive vs. non-eruptive - and are weighted differently helping to removeline-of-sight ambiguity. By utilizing testbeds of syntheticdata at all wavelengths (from radio to extreme ultraviolet),effective measurement and optimization strategies can bedeveloped which will set priorities and for future observa-tional development.
Status:
DKIST will provide opportunities for polarime-try and testing of observational techniques with high reso-lution and sensitivity but in a small (5 arc minute) field ofview. Proposed new observations include large (1.5 meter) ground-based coronagraph(s) with narrow-band filter po-larimeter and spectropolarimeter to observe the full Suncorona at the limb in the visible and infrared (currently un-dergoing engineering design and preliminary design reviewas US-China collaboration). Space-based missions wouldprovide better duty cycle and continuity of measurementsthan ground-based, and also would allow measurement atshort wavelengths otherwise blocked by the Earth’s atmo-sphere. Mission concepts have been proposed (ESA) withinstruments including spectropolarimetric coronagraphs inthe EUV and IR for off-limb observations, and spectropo-larimeters to observe the solar disk at heights from thecorona down into the chromosphere.
Appendix F.7. Auroral imaging to map magnetosphericactivity and to study couplingRationale:
The response of magnetosphere to solar winddriving depends on the previous state of magnetosphere.Similar sequences in energy, momentum and mass transferfrom the solar wind to magnetosphere can lead in somecases to events of sudden explosive energy release whilein other cases the dissipation takes place as a slow semi-steady process. Comprehensive understanding on the fac-tors that control the appearance of the different dissipa-tion modes is still lacking, but obviously global monitoringof the magnetospheric state and system level approach inthe data analysis would be essential to solve this puzzle.Continuous space-based imaging of the auroral oval wouldcontribute to this kind of research in several ways. The sizeof polar cap gives valuable information about the amountof energy stored in the magnetic field of magnetotail lobes.Comparison of the brightness of oval at different UV wave-lengths yields an estimate about the energy flux and av-erage energy of the particles, which precipitate from themagnetosphere to the ionosphere. These estimates are notas accurate as those from particle instruments onboardLEO satellites, but the additional value comes from thecapability to observe all sectors of the oval simultaneouslyand continuously. Such view is useful especially in thecases where the magnetosphere is prone to several subse-quent activations in the solar wind. The shape and sizeof the oval and intensity variations in its different sectorsenable simultaneous monitoring of, e.g., nightside magne-tospheric recovery from previous activity, while new energyalready enters the system from a new event of dayside re-connection.
Objectives:
To achieve continuously global UV-imagesto follow the morphology and dynamics of the auroral oval,at least in the Northern hemisphere, but occasionally alsoin the southern hemisphere. Imager data combined withground-based SuperDARN and SuperMAG networks al-lows solving the ionospheric Ohm’s law globally, whichyields a picture of electric field, auroral currents and con-ductances with good accuracy and sufficient spatial reso-lution. This would mean a leap forward in our attemptsto understand M-I coupling, particularly the ways how58onospheric conditions control the linkage to the magne-tosphere by, e.g., by field-aligned currents.
Key requirements:
An imager which can observe theelectron auroral emissions in the Lyman-Birge-HopfieldNitrogen waveband, discriminating between the LBH-longand LBH-short bands. This set-up provides informationabout precipitating electrons in the range 1-20 keV. Forsolving the ionospheric electrodynamics (by estimation ofionospheric conductances) also an imager for Bremsstrah-lung radiation (more energetic electrons, 20-150 keV) wouldbe necessary. For proton precipitation the mission wouldneed an imager capable to capture Doppler-shifted Lyman-emission from charge-exchanging precipitating protons. Timeresolution of the images should be better than 60 sec andspatial resolution should reach ∼
50 km (at perigee)
Implementation:
The objective of continuous monitor-ing can be achieved with a constellation of two identically-instrumented spacecraft in identical highly-elliptical polarorbits (apogees close to 7 RE above the northern pole andperigees near 2 RE.). The orbits of the two spacecraftshould be phased so that one spacecraft is at perigee whilethe other is at apogee and the imagers onboard should beable to observe the auroras from both positions.
Status:
Undergoing more detailed definition within in-ternational science teams
Supporting observations:
Global ground-based networks,existing LEO and GEO satellites, existing mid-tail con-stellation missions, and - as always - upstream solar windmonitor.
Appendix F.8. Observation-based radiation environmentmodelingRationale:
The radiation belts are key domains in theEarth’s magnetosphere, which cause spacecraft anomalies.It is essential for satellite operators to know if relativisticelectrons can be expected to show a major increase, whichis related to the high risk of spacecraft anomalies. Thusprocesses of acceleration, transport, and loss of energeticelectrons should be the basis for predicting the dynam-ics of trapped energetic particles. However understand-ing radiation-belt dynamics is a major shortfall in cur-rent theoretical understanding. Currently understandingof Energetic Electron and Proton acceleration mechanismsis insufficient to discriminate between the effectiveness ofdifferent energisation, transport and loss processes at dif-ferent L-shells and local times.Trapped energetic particles in the inner magnetosphereform radiation belts. The inner proton belt is stable, butthe outer radiation belt comprises a highly variable pop-ulation of relativistic electrons. Solar wind changes pro-duce changes to trapped particle transport, acceleration,and loss. However the pre-existing magnetospheric stateis also a critical factor. For example efficient productionmechanisms appear to need a seed population of energeticelectrons. Relativistic electrons enhancements are an im-portant space weather factor with a strong influence on satellite electronics. Around 50% of magnetic storms arefollowed by a corresponding enhancement of relativisticelectron fluxes.Storm-time magnetospheric convection intensification,local particle acceleration due to substorm activity, reso-nant wave-particle interaction are the main fundamentalprocesses that cause particle fluxes energisation and loss.However, the details of the mechanisms that may be ableto contribute to these processes remain a subject for activeresearch. While progress has been made in the theoreti-cal understanding of these competing processes, there is asyet no clear consensus on which of these will be significantin particular situations, and no real predictive methodswhich can give precise fluxes at different local and univer-sal times. There is therefore a pressing need to confronttheoretical models with detailed measurements, in orderto resolve these shortfalls. Quantitative assessment of thepredictive properties of current and emerging models isthus essential. Hence detailed testing against fine-grainedobservations is needed.At the onset of most geomagnetic storms the outerzone of the radiation belts may be depleted in severalhours. Subsequently, the outer zone will some times buildup to levels higher than before the magnetospheric activ-ity began. A variety of processes can apply in differentconditions (see MEP1), with more extreme events sometimes causing prompt effects. There is no clear correla-tion between ring current enhancement, as measured byDst, and the effects in terms of relativistic electron pen-etration deeper into the outer zone, slot, and even innerzone. In the past it was believed that the higher the so-lar wind speed, the more likely is the event to lead toelevated post-event electron fluxes; however this has re-cently been called into question. Monitoring such eventsat GEO is routinely undertaken. Given the very limitedunderstanding of radiation-belt dynamics currently avail-able (see above), the current consensus is that excellentmonitoring of the real time environment (nowcasting) isthe most useful product that can be provided to satel-lite operators. This, and well characterized descriptionsof historical events, can be used to interpret failures andimprove the resilience of spacecraft design.
Objective:
In-situ multipoint measurements of relativis-tic and sub-relativistic electrons in the inner magneto-sphere, at least at GEO to control radiation belt particlepopulations, at different times, L-shells and local times.Continuous control of the geomagnetic activity indices (es-pecially Dst) and solar wind conditions (velocity, field ori-entation and pressure) to predict the possible relativisticelectron fluxes variations. Realistic models capable of pre-dicting the radiation belts dynamics can be constructed af-ter detailed testing against fine-grained observations. Sucha model (or models) will have provided a realistic basis forimproved engineering designs and procedures, which mit-igate potential impacts.
Key requirements:
Multi-point in-situ observations andreal-time analysis of energetic particle fluxes (mostly, 0.159 10 MeV for electrons) in the inner magnetosphere, of thecurrent geomagnetic conditions (mostly, Dst and AL in-dices) and solar wind / IMF conditions at L1 point.
Implementation concepts:
To realize our objectives, main-taining the current observation facilities related to radia-tion belt dynamics (particle and electromagnetic field mea-surements in the inner magnetosphere is essential). Tofill the gap of observational data, hosting radiation mon-itor payloads (and/or cubesat missions) at LEO, MEO,GEO, and constructing new ground-based observatoriesfor sparsely covered region is also encouraged. Models (em-pirical, theoretical, numerical) which are based on theseobservational data will improve our understanding of trans-port, acceleration, and loss processes in the radiation belt.Establishing methodologies and metrics for validation andcalibration of models and data is another important issue.
Status:
Continuing observations of energetic particlesfrom LANL, GOES, ELECTRO-L, POES, Meteor-M. Ge-omagnetic indices from WDCs. Solar wind parametersfrom L1 (ACE).
Supporting observations:
The current constellation ofCluster, Van Allen Probes, THEMIS, with the upcomingMMS, along with data from the geostationary satellites,and ground-based observation networks by magnetometersand HF radars represent a perfect opportunity to achievea major step forward. Theoretical studies and modeling isunderway. What is needed is investment in a few minorexpansions and in particular international coordination topush the program forward.
Appendix F.9. Solar energetic particles in the inner he-liosphereRationale:
SEPs present a major hazard to space-basedassets. The strong increases in fluxes of high-energy pro-tons, alpha particles and heavier ions can cause or con-tribute to a number of effects, including tissue damage forastronauts, increases in radiation doses, single event ef-fects (SEEs) in micro-electronics, solar cell degradation,radiation damage in science instruments and interferencewith operations. In addition, large SEP events can alsoaffect aviation, through increases in radiation dose levelsand interference with avionics through SEEs.The production of SEPs is associated with large flaresand fast CMEs in the low corona, typically originatingfrom complex active regions. The prompt response canarrive at Earth in less than an hour from the onset oferuption, and some times in a few minutes after that on-set in the case of a well-connected, relativistic particleevent. This is followed by a longer lasting, often rising,flux of particles originating at the CME shock as it prop-agates through the heliosphere, and a short sharp veryhigh flux of energetic storm particles (ESPs) as the CMEshock passes the point of measurement. While warning ofevents in progress is certainly important, many users re-quire significantly longer warning, e.g., 24 hours (e.g., for(e.g., all-clear periods for EVAs for astronauts). At the onset of major (M or X) class flares and fastCMEs, relativistic SEPs (GeV protons) can arrive minutesafter the start of the event in the case of a well-connectedevent. Less energetic protons will arrive minutes to hourslater depending on the energy but also on the propaga-tion in the interplanetary medium. Recent multi-pointobservations of SEP events off the Sun-Earth line (STE-REO observations) furthermore show that prompt ener-getic particles have access to a wide longitudinal extentfor some events. Recent studies also show that for a largeproportion of SEP events, the prompt energetic particlesdo not propagate along the normal Parker spiral but in themagnetic field of a pre-existing CME. All this representsan additional difficulty for the forecasting of the arrivalof SEPs at Earth, since in addition to the conditions ofdiffusion in the medium, this affects the delay betweenproduction of energetic particles and arrival at the earth.On the other hand, shocks produced by fast CMEs startto be identified in coronagraph images.Energetic storm particles (ESPs) can also reach >
500 MeVand also pose major space weather hazard. They representa “delayed” radiation hazard and the ESP event forecastis essentially a shock arrival forecast. A good indicator ofan ESP event is thus a radio-loud shock, i.e. a shock thatproduces type II radio burst near the Sun and the inter-planetary medium. Shock travel time ranges from about18 hours to a few days, so there is a good chance of mak-ing prediction of ESP events. However, the main questionis how the intensity, duration, and arrival time dependson the SEP event near the Sun, presence of a type II ra-dio burst in the near-Sun interplanetary medium, and thesource location of the CME that drives the shock. ESPevents are generally of low energy, so they are expected toprecipitate in the polar region. Thus, they are hazardousto satellites in polar orbits. They lead to radio fadeouts inthe polar region and may cause communication problemsfor airplanes in polar routes.
Objectives:
In addition to the objectives for solar ob-servations of active regions and of the solar global coronaand of the inner heliosphere from a perspective off the Sun-Earth line (7.1) obtain multi-point in-situ observations ofSEPs off the Sun-Earth line and possibly closer than theL1 distance.
Key requirements:
Multi-point in situ observations ofSEPs off the Sun-Earth line and possibly closer than theL1 distance.
Implementation concept:
Suite of sensors measuringelectrons, protons, and ions from helium to iron in thekeV to over 100 MeV per nucleon range.
Status:
Continuing observations of energetic particlesfrom STEREO, ACE, and other platforms. Upcoming So-lar Orbiter and Solar Probe Plus missions will provide keymeasurements of SEPs close to the acceleration region.Different concepts of missions at L5 proposed (NASA so-lar and space physics road map, ESA/CAS small missionopportunity, ...) Development of solar sails would open upnew research opportunities for energetic particle science60nd monitoring.
Supporting observations:
Continuing operations of ground-level neutron monitors and near real-time access to data ofthese observatories. They provide information on the ar-rival of the most energetic protons from flares. Radio ob-servations (ground-based and satellite) of electron beamsand shocks propagating in the interplanetary medium. Also:continued analysis of radio-nuclide data in biosphere, icecores, and in terrestrial and lunar rocks, as these provideinformation on pre-historical extreme events that cannototherwise be obtained. Use of multiple data sources andradio-nuclides helps to provide some information on par-ticle energy spectra that are needed to better constrainfluences and to specify environmental conditions.
Appendix G. Acronyms - ACE Advanced Composition Observatory- AIA SDO’s Atmospheric Imaging Assembly- AMPERE Active Magnetosphere and Planetary Electro-dynamics Response Experiment- AOGS Asia Oceanea Geosciences Society- ARTEMIS Acceleration, Reconnection, Turbulence andElectrodynamics of the Moon’s Interaction with the Sun- ASPOC Active Spacecraft Potential Control Experiment(on board Cluster)- AU astronomical unit (Sun-Earth distance)- BBF bursty bulk flow- CAS Chinese Academy of Sciences- CCMC Community Coordinated Modeling Center- CEDAR coupling, energetics, and dynamics of atmo-spheric regions program- CIP critical infrastructure protection- CME coronal mass ejection- COPUOS UN Committee on the Peaceful Uses of OuterSpace- COSMIC Constellation Observing Sysgtem for Meteorol-ogy, Ionosphere, and Climage- COSMO Coronal Solar Magnetism Observatory (in MLSO)- COSPAR ICSU’s Committee on Space Research- CSRH Chinese Spectral Radio Heliograph- DHS Department of Homeland Security- DKIST Daniel K. Inouye Solar Telescope- DMSP defense meteorological satellite program- DSCOVR deep-space climate observatory- Dst disturbance storm time index- EGNOS European Geostationary Navigation Overlay Ser-vice- EGU European Geophysical Union- EISCAT European Incoherent Scatter Scientific Associ-ation- ERG Exploration and energization of Radiation in Geo-space- ESA European Space Agency- ESP energetic storm particle(s)- ESPAS European strategy and policy analysis system - EU European Union- EUV extreme ultra violet- eV electron-Volt- FAC field-aligned current- FASR Frequency-Agile Solar Radio telescope- FPI Fabry-Perot interferometer(s)- FR Faraday rotation- GB ground-based- GBO ground-based observatory- GCR galactic cosmic ray(s)- GEM geospace environment modeling program- GEO geostatioinary orbit- GeV gigaelectron-Volt- GIC geomagnetically induced current- GLE ground-level enhancement- GMD geomagnetic disturbance- GNSS global navigation satellite system- GOES Geostationary Operations Environmental Satellite- GOLD Global-scale Observations of the Limb and Disk- GONG The Global Oscillation Network Group in NSO- GPS Global Positioning System- GTO geostationary transfer orbit- H2020 Horizon 2020, funding program of EU for researchand innovation- HELIO heliophysics integrated observatory- HF high frequency- IAU International Astronomical Union- ICON The Ionospheric Connection mission- ICSU International Council for Science- ICTSW Interprogramme Coordination Team on SpaceWeather of WMO- IDL Interactive Data Language- IGY International Geophysical Year 1957-58- ILWS International Living With a Star program- IPS interplanetary scintillation- IR infra-red- ISES International Space Environment Service- ISR incoherent scatter radar- iSWA Integrated Space Weather Analysis System (NASA)- ITM ionosphere-thermosphere-mesosphere- IUGG International Union of Geodesy and Geophysics- IUGONET Inter-university upper atmosphere global obs-ervation network- JAXA Japan Aerospace eXploration Agency- JCSDA Joint Center for Satellite Data Assimilation- KAIRA Kilpisj¨arvi Atmospheric Imaging Receiver Array- keV kilo electron volt- L1 Lagrangian point 1- L5 Lagrangian point 5- LANL Los Alamos National Laboratories- LASCO Large Angle and Spectrometric Coronagraph- LBH Lyman-Birge-Hopfield Nitrogen waveband- LEO low-Earth orbit- LF low frequency- LOFAR Low-Frequency Array for Radio astronomy- LORAN Long Range Navigation- LOS line-of-sight61 LWS NASA/SMD Living With a Star program- MeV megaelectron-Volt- MEO medium Earth orbit- MDI Michelson Doppler Imager (on SoHO)- MHD magneto-hydro-dynamic- MI magnetosphere-ionosphere- MHD magnetohydrodynamic- MIT magnetosphere-ionosphere-thermosphere- MMS magnetospheric multi-scale mission- MLSO Mauna Loa Solar Observatory- MLTI magnetosphere-lower thermosphere-ionosphere- MMS magnetospheric multi-scale- MSAS MTSAT satellite based augmentation system- MSIS Mass Spectrometer and Incoherent Scatter Radar(empirical atmosphere model)- MTSAT Multi-functional Transport Satellite- MUF maximum usable frequency- NASA National Air and Space Administration- NERC US National Energy Regulatory Commission- NRT near real time- NOAA US National Oceanographic and Atmospheric Ad-ministration- NSF National Science Foundation- NSO US National Solar Observatory- OSCAR Observing Systems Capability Analysis and Re-view Tool of WMO- OSTP Office of Science and Technology Policy- PCW Polar Communications and Weather satellite sys-tem- POES polar operational environmental satellite- PFSS potential-field source-surface model- PSW ICSU/COSPAR panel on space weather- R2O research-to-operations- RB radiation belt- RBSP Radiation Belt Storms Probes- R E Earth radius of 6371 km- REP relativistic electron precipitation- RTK Real Time Kinematic- SAA South Atlantic anomaly- SAMA South Atlantic magnetic anomaly- SAPS sub-auroral polarization streams- SAR synthetic aperture radar- SBAS space-based augmentation system- SCW substorm current wedge- SDO Solar Dynamics Observatory- SEE single event effect(s)- SEP solar energetic particle(s)- SEU single-event upset- SMD NASA’s science mission directorate- SHINE solar, heliosphere, and interplanetary environ-ment program- SKA Square Kilometer Array- SMEX NASA SMall EXplorer- SOAP Simple Object Access Protocol- SoHO Solar and Heliospheric Observatory- SOLIS Synoptic Optical Long-term Investigations of theSun (NSO) - SPASE space physics archive search and extract- SPE solar particle event- SPP Solar Probe Plus (NASA mission)- SSA space situational awareness- SSI solar spectral irradiance- STEREO Solar-Terrestrial Relations Observatory- SuperDARN Super Dual Auroral Radar Network- SWPC US/NOAA Space Weather Prediction Service- SWx space weather- TEC total electron content- THEMIS time history of events and macroscale interac-tions during substorms- TID traveling ionospheric disturbance(s)- UCAR university corporation for atmospheric research- UN United Nations- WAAS wide area augmentation system- WDC World Data Center of ICSU- WDS World Data System of ICSU- WMO World Meteorological Organization
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