Hanna Rothkaehl

Discovering the sky at the Longest Wavelengths (DSL)

The radio sky at frequencies below ~30 MHz is virtually unobservable from Earth due to ionospheric disturbances and the opaqueness of the ionosphere below ~10MHz, and also due to strong terrestrial radio interference. Deploying a radio observatory in space would open up this largely unexplored frequency band for science in astronomy, cosmology, geophysics, and space science. A Chinese-European team is proposing an ultra long wavelength (ULW) radio interferometer mission DSL (Discovering the Sky at the Longest Wavelengths). The proposed radio interferometer will be deployed in low-altitude lunar orbit, exploiting the radio quietness of the lunar far side. DSL will consist of a mother-spacecraft for data transport and control, plus eight small micro-satellites each equipped with three orthogonal dipoles. These satellites form a virtual distributed observatory with adjustable baselines, allowing different scientific observation strategies. The satellites are configured in a flexible quasi-linear array in nearly identical orbits, guaranteeing low relative drift rates. Short orbital periods and orbit precession ensure quick filling of the interferometric spatial frequency (u, v, w) space, enabling high quality imaging. The science themes considered for the DSL mission include pioneering studies of the unknown and exploratory science such as the search for signatures of the cosmological Dark Ages, complementing current (e.g. LOFAR) and future SKA telescope searches; full-sky continuum survey of discrete sources, including ultra-steep spectrum extragalactic sources, pulsars, and transients (galactic and extragalactic); full-sky map of continuum diffuse emission; solar-terrestrial physics, planetary sciences, and cosmic ray physics. The main frequency band covered is 1-30 MHz extending down to 0.1 MHz, and up to about 50 MHz for cross-referencing with ground-based instruments. DSL will support a variety of observational modes, including broad-band spectral analysis for Dark Ages, radio interferometric cross-correlations for imaging, and flexible raw data downlink capability. Data processing will be performed at radio astronomy science data centres in Europe and China.

Low Altitude Cusp–Cleft Region Signatures of Strong Geomagnetic Disturbances

The polar cusp being a region of the free access of the solar wind into the inner magnetosphere is also the site of turbulent plasma flow. The cusp area at low altitudes acts like a focus of a variety type of instability and disturbances from different regions of the Earth. Daily f0F2 frequencies are discussed regarding the cusp position. The high time resolution wave measurements together with electron and ion energetic spectra measurements registered on the board the Freja satellite and Magion-3 and the electron density at the peak of f0F2 layers collected from ground-based ionosonde measurements were used to study the response of ionospheric plasma within the cusp–cleft region to the strong geomagnetic storm. In this paper we present the response of the ionospheric plasma to the disturbed conditions seen in the topside wave measurements and in the ionospheric characteristics maps obtained from the ground-based VI network. The need of the cusp feature model for radio communication purposes is advocated.

Prospects for Solar and Space Weather Research with Polish Part of the LOFAR Telescope

The LOw-Frequency ARray (LOFAR) is a new radio interferometer that consists of an array of stations. Each of them is a phase array of dipole antennas. LOFAR stations are distributed mostly in the Netherlands, but also throughout Europe. In the article we discuss the possibility of using this instrument for solar and space weather studies, as well as ionosphere investigations. We are expecting that in the near future the LOFAR telescope will bring some interesting observations and discoveries in these fields. It will also help to observe solar active events that have a direct influence on the near-Earth space weather.

POLFAR - Polish incarnation of the LOFAR. Scientific objectives and system realization

Polish astronomers and space scientists are participating in the development and use of a radio astronomical instrument of new generation: Low Frequency ARray - LOFAR, exploring yet poorly studied range of low (<;300 MHz) frequencies. It constitutes a European array of thousands of antennas - a challenge for data transfer and processing techniques. The LOFAR facilities in Poland will be distributed among three sites: Lazy (East of Kraków), Borówiec near Poznań and Baldy near Olsztyn. All they will be connected via PIONIER dedicated links to Poznań. Each site will host one LOFAR station (96 high-band+96 low-band antennas). They will most time work as a part of European network, however, when less charged, they can operate as a national network. LOFAR will study objects in early Universe (like the high-redshift neutral hydrogen) and cosmic plasma in conditions unreachable in earth-based laboratories: densities either very high (pulsars) or extremely low, temperatures ranging from single Kelvins to milions of degrees and a wide range of magnetic field strengths. This research is important for Sun-Earth system plasma monitoring and for plasma technologies. To fulfill the conditions to participate in LOFAR Polish astronomers established the national consortium - POLFAR which also will hosting reference stations for the Global Navigation Satellite System (GNSS).

Seasonal Variations of Mid-Latitude Ionospheric Trough Structure Observed with DEMETER and COSMIC

The mid-latitude ionospheric trough is a depleted region of ionospheric plasma observed in the topside ionosphere. Its behavior can provide useful information about the magnetospheric dynamics, since its existence is sensitive to magnetospherically induced motions. Midlatitude trough is mainly a night-time phenomenon. Both, its general features and detailed characteristics strongly depend on the level of geomagnetic disturbances, time of the day, season, and the solar cycle, among others. Although many studies provide basic information about general characteristics of the main ionospheric trough structure, an accurate prediction of the trough behavior in specific events is still understood poorly. The paper presents the mid-latitude trough characteristics with regard to the geomagnetic longitude and season during a solar activity minimum, as based on the DEMETER in situ satellite measurements and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements.

New advanced radio tools for monitoring and diagnostics near Earth plasma environment

To give a more detailed and complete understanding of physical plasma processes that govern the solar terrestrial space, and to develop qualitative and quantitative models of the magnetosphere ionosphere thermosphere coupling, it is necessary to design and build the next generation of instruments for space diagnostics and monitoring. Novel ground based wide area sensor networks, such as the LOFAR (Low Frequency Array) radar facility, comprising wide band, and vector sensing radio receivers and multi-spacecraft plasma diagnostics should help solve outstanding problems of space physics and describe long-term environmental changes. The LOw Frequency ARray LOFAR is a new fully digital radio telescope designed for frequencies between 30 MHz and 240 MHz located in Europe. The three new LOFAR stations will be installed until summer 2015 in Poland. The LOFAR facilities in Poland will be distributed among three sites: Lazy (East of Krakow), Borowiec near Poznan and Baldy near Olsztyn. All they will be connected via PIONIER dedicated links to Poznan. Each site will host one LOFAR station (96 high band 96 low band antennas). They will most time work as a part of European network, however, when less charged, they can operate as a national network The new digital radio frequency analyzer (RFA) on board the low orbiting RELEC satellite was designed to monitor and investigate the ionospheric plasma properties. This two-point ground-based and topside ionosphere located space plasma diagnostic can be a useful new tool for monitoring and diagnosing turbulent plasma properties. The RFA on board the RELEC satellite is the first in a series of experiments which is planned to be launched into the near Earth environment. In order to improve and validate the large scales and small scales ionospheric structures we will used the GPS observations collected at IGS/EPN network employed to reconstruct diurnal variations of TEC using all satellite passes over individual GPS stations and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements. The main purpose of this presentation is to describe new advanced diagnostic techniques of the near Earth space plasma and point out the scientific challenges of the radio frequency analyser located on board of low orbiting satellites and LOFAR facilities.

The main ionospheric trough behavior seen from the in-situ and radio measurements

The main ionospheric trough (MIT) is large structure observed in mid-latitude area of Earths ionosphere. It is depleted region of ionospheric plasma typical for the topside ionosphere, especially F layer, where electron density level can significantly decrease as compared to densities measured for adjoining sub-auroral and equatorial regions. The MIT itself and its variability strongly affect the propagation of different natural and artificial signals thus its characteristic is important for radio communication and for communication and space industry in general. We compared data from in-situ measurements collected onboard DEMETER satellite and electron density profiles obtained from radio occultation method used by FORMOSAT-3/COSMIC mission to study the nature of MIT and its behavior during different seasons and magnetic conditions. This paper presents the results obtained in both geographic and magnetic system at fixed local time.

TwinCube—Preliminary Study of a Tether Experiment for CubeSat Mission

The article covers a preliminary research on a Tethered Satellite System based on a 3U CubeSat pico-satellite standard, which main purpose is to perform two-point diagnostic measurements of electromagnetic emissions in near-Earth plasma. Multi-point measurements play a significant role in understanding energy flows driven by Sun as well as terrestrial activity. Since CubeSats are expected to be low-cost and robust, development of a small and efficient plasma diagnostic tool for hardware-restrained CubeSat platform might be important also for future space cluster missions. We propose a TwinCube mission consisting of two sub-satellites that will be preliminarily bonded with lock-and-release mechanisms. During in-orbit operations the mechanism will be released allowing for unwinding of the non-conductive tether and for separating two sub-satellites for up to 1 km. This action is crucial for the mission success and is considered as one of the important technological aspects of the project. Objectives and justification of the mission are outlined in the article, together with basic mission scenario, simulations confirming feasibility of the idea and discussion on assumptions for the mechanical design.

Juice -ESA mission to Jupiter and the Polish contribution

The JUpiter ICy moons Explorer (JUICE) will perform advanced investigations of Jupiter and its system in order to understand their inter-relations and complexity. The special attention will be focus on investigation related to the definition the Ganymede as potential habitat. However investigations of Europa and Callisto would complete a comparative picture of the Galilean moons. JUICE is the necessary step for future exploration of Solar System. The JUICE mission was selected by ESA in May 2012, as a first large mission within the Cosmic Vision Program 2015-2025. As Jupiter is the archetype for the giant planets of the Solar System deeply understanding this system its history, from its origin to the possible emergence of habitable environments, will give us unique possibilities for basic research as well as for exploration and advanced technical development. The JUICE mission has been formulated with consultation and strong support from the international planetary science community and it will have broad appeal across a number of different disciplines including geologists, astrobiologists, magnetospheric and atmospheric scientists. The Radio & Plasma Waves Investigation (RPWI) consists of a highly integrated instrument package that will carry out measurements that allow for comprehensive science investigations of the space environments around Jupiter primarily near Ganymede, Europa and Callisto, as well as monitoring radio wave emissions in the Jupiter system.

Integration of multi instrument ionospheric plasma diagnostics used for near Earth environmental modelling

In order to enhance our understanding of the rich plasma physical processes that drives the solar-terrestrial space environment we need to dramatically increase our ability to perform multi point measurements with sensors of different types. The magnetosphere-ionosphere-thermosphere system is strongly affected by electric and magnetic fields, particle precipitation, heat flows and small scale interactions. The changes of the near Earth plasma conditions are produced mainly by natural perturbations, but some of them also have anthropogenic origin. The diagnostics of the ionospheric plasma property as electron and ion density, temperature and velocity can provide essential inputs for modeling the Space Weather conditions. The aim of this presentation is to show global distribution of main plasma parameters during different geomagnetic conditions and seasons diagnosed by various measuring techniques as: in situ wave and plasma diagnostics registered on board of DEMETER satellite, GPS observations collected at IGS/EPN network, GPS observation carried out at the Antarctic and Arctic IGS (International GNSS Service) stations used and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements. We are willing to present and validate the properties of the ionospheric electron density profiling retrieved from FORMOSAT-3/COSMIC radio occultation measurements. The comparison of radio occultation data with ground-based measurements indicates that usually COSMIC profiles are in a good agreement with ionosonde profiles both in the F2 layer peak electron density (NmF2) and the bottom side of the profiles. For this comparison ionograms recorded by European ionospheric stations (DIAS network) during 2008 year were used. We would like also to discuss the limitation of presented diagnose techniques with respect to different geomagnetic condition and localisation in space.