Gary Heckman

Panel achieves consensus prediction of solar cycle 23

In September 1996, a panel of experts on solar cycle prediction techniques met in Boulder, Colorado, to survey forecasts of solar and geomagnetic activity and to arrive at a consensus on how the solar cycle will develop. After two weeks of deliberation, the panel of 12 scientists (from Australia, Germany, the United Kingdom, and the United States) agreed that a large amplitude solar cycle with a smoothed sunspot maximum of approximately 160 is probable near the turn of the century. The amplitude of the predicted cycle is comparable to that of the previous two solar cycles (see Figure 1). Our ability to predict solar and geomagnetic activity is crucial to many technologies, including the operation of low-Earth orbiting satellites, electric power transmission grids, geophysical exploration, and highfrequency radio communications and radars. Because the scale height of Earths upper atmosphere (and thus the drag on satellites in low Earth orbit) depends on the levels of short-wavelength solar radiation and geomagnetic activity, we need to know the profile and magnitude of the next solar and geomagnetic cycle in order to plan for reboosting the Hubble Space Telescope and assembling the International Space Station.

Prediction and evaluation of solar particle events based on precursor information

Protection from the radiation effects of solar particle events for deep space mission crews requires a warning system to observe solar flares and predict subsequent charged particle fluxes. Such a system relates precursor information observed in each flare to the intensity, delay, and duration of the subsequent Solar Particle Event (SPE) at other locations in the solar system. A warning system of this type is now in operation at the NOAA Space Environment Services Center in Boulder, Colorado for support of space missions. It has been used to predict flare particle fluxes at the earth for flares of Solar Cycle 22. The flare parameters used and the effectiveness of the current warning system, based on Solar Cycle 22 experience, are presented, with an examination of the shortcomings. Needed improvements to the system include more complete observations of solar activity, especially information on the occurrences of solar mass ejections; and consideration of the effects of propagation conditions in the solar corona and interplanetary medium. Requirements for solar observations and forecasting systems on board the spacecraft are discussed.

GOES solar x-ray imager: overview and operational goals

The first solar x-ray imager (SXI) will provide a major advance in real-time, continuous monitoring of solar- terrestrial conditions. This instrument, which will fly on a Geostationary Operational Environmental Satellite (GOES), will provide full-disk images of the Sun once a minute in the 0.6-6 nm range with 5 arcsec pixels. SXIs images will complement x-ray fluxes from the disk-integrating GOES x-ray sensor and optical images from ground-based observatories. THe automated sequence of SXI images will make it easy for forecasters, researchers, and image processing algorithms to interpret the images. SXI is being built to meet five operational goals for real-time prediction of solar- terrestrial disturbances: 1) SXI will provide clear evidence of x-ray coronal holes that are associate with recurrent geomagnetic storms. 2) SXI will provide flare locations that are used to estimate the magnitude and timing of energetic particle events, including flares from regions behind the solar limb that are not visible at other wavelengths. 3) SXI could provide a significant improvement in forecasting geomagnetic disturbances if CME-associated brightenings can be readily observed. 4) SXI images will show the complexity of the active regions, which will be used to estimate each regions flare potential.

Solar and geomagnetic activity during cycle 21 and implications for cycle 22

Old Cycle 21 ended and new Cycle 22 began in September 1986. As measured by its sunspots, the new cycle of solar activity is rising more rapidly than any previous cycle in the records dating back to 1755 A.D. Progress of the new cycle—expected to last about 11 years—is of interest because terrestrial satellite missions and other technical systems are affected by various forms of solar activity; all forms of activity rise more or less in concert with the sunspots of the new cycle. In consequence, the solar output also varies. For example, the slowly varying background ultraviolet flux varies, affecting the density of the terrestrial thermosphere. In turn, satellite drag and radio propagation effects vary. Flares, energetic solar proton events, and geomagnetic storms occur in cycles that begin and end about the same time as the sunspot cycle but do not track it as well as t h e slowly varying radiation. The exceptionally rapid rise of the new cycle is the basis for prediction of a cycle of record amplitude with smoothed sunspot numbers ∼200 and smoothed 10.7-cm solar radio flux ∼250, which would equal or exceed the largest cycles of the past. Cycle 19, the largest recorded, peaked in 1958 with a smoothed sunspot number of 201. Methods based on observation of antecedent phenomena in Cycle 21 predict that Cycle 22 will have a large maximum sunspot number well above average but not record equaling. At the present time, there is no consensus regarding which group of predictions is likely to be the more valid. Nonetheless, it appears increasingly likely that Cycle 22 will reach a peak sunspot number well above the average of all previous cycles. In another 6–12 months we expect to have a better idea of the maximum yet to come.

The monitoring and prediction of solar particle events — An experience report

The routine monitoring and prediction of solar proton events that may be a hazard to personnel and materials in space are a routine service of the Space Environment Services Center in Boulder, Colorado, U.S.A. The services provided are made available to the space centers in the United States for use in their operations. The real time monitoring consists primarily of Space Environment Monitors on both geosynchronous and polar orbiting weather satellites. The monitoring emphasizes proton fluxes but alpha particles, electrons, and in one case, heavier particles, are included. The predictions are of two types; a general outlook made 1 to 3 days in advance, and specific prediction of event size and probability of occurrence made after a solar flare occurs. The accuracy of the prediction made for solar cycle 21 are assessed.

NOAA Space Environment Center mission and the GOES space environment monitoring subsystem

The mission of the NOAA Space Environment Center (SEC) is to serve the nations need to reduce adverse effects of solar- terrestrial disturbances on humankinds activities. To meet this need, SEC: 1) acquires, interprets, and disseminates space weather information; 2) prepares and disseminates forecasts and alerts of conditions of the space environment; 3) conducts research and development in solar-terrestrial physics and in techniques to improve monitoring and forecasting; 4) prepares high quality data for national archives; 5) uses its expertise to advise and educate those affected by variations in the space environment. Users are provided information in the form of forecasts, nowcasts, data, advice, support, expertise, and publications about conditions in the solar-terrestrial environment. The space environment monitors on GOES spacecraft provide space weather observations from the Sun to Earth and form the basis of the SEC real-time operation. The X-ray sensor (XRS) monitors solar flare activity and serves as the international standard for rating the intensity of flares. Flares are observed and classified according to the intensity of their emission on the XRS sensor. Forecasts of the occurrence of solar flares are expressed in terms of the measurements from the XRS. SEC also issues a daily index of the background solar radiation based on the XRS measurements. SOlar particle events (SPE) and energetic electron event s are detected using the energetic particle sensor (EPS) on GOES. Alerts and forecasts of the occurrence of SPE are made in terms of the fluxes of charged ions (mostly protons) measured by the EPS. Alerts are issued for energetic electron events based on the EPS measurements.

Space environment monitoring mission beyond GOES-M

Conditions in the near-Earth space environment are of every increasing importance to our human activities on Earth and in space. The provision of the space environment services required in future depends on improving our understanding of solar activity and the coupling of this activity to our local region of space, as well as improving our remote sensing and in-situ monitoring of conditions and events in the solar system. Our present service is largely analogous to the state of terrestrial weather forecasting rom a local weather office before the advent of numerical modeling and remote atmospheric sensing technology. Numerical models of the local space environment and of interplanetary space are being developed. However, these models are limited in performance by our understanding of the underlying physical processes, and their practical applications is restricted by the paucity of observational data. Instruments on the GOES provide a critical resource to NOAAs space environment services. GOES is our most effective operational platform for real-time remote sensing of the Sun, the near-Earth environment, and processes in interplanetary space. It also makes important in-situ measurements in a critical region of space that is now of huge commercial importance. This paper will discuss the planned and potential extensions of the GOES space environment monitor in the overall context of the data required to meet the future needs for space environment services.

Solar cycle 22 continues strong climb

Solar Cycle 22, which began in September 1986, continues to rise at a rate that rivals or exceeds that of all sunspot cycles in the record of direct sunspot observations. As measured by smoothed sunspot numbers and 10.7-cm radio flux values, Cycle 22 remains ahead of all past cycles in the modern record except Cycle 19, which peaked during the late 1950s (see Figure 1). By other measures, such as the number of X ray flares or solar proton events, this cycle is running up to 30% higher than at the corresponding point in all previous cycles. In our previous report (“Solar and Geomagnetic Activity During Cycle 21 and Implications for Cycle 22,” Eos, 69, 962, 1988) we presented early information on Cycle 22 and discussed some possible solar-terrestrial effects of solar activity. Figure 1 updates that information to the present in sunspot number and 10.7-cm radio flux values.

Strategies for dealing with solar particle events in missions beyond the magnetosphere

For long duration missions beyond the magnetosphere, the hazards posed by solar particle events (SPE) require the development of new strategies to minimize both the radiation dose and the effects. Potential strategies include the development of improved short-term forecasting of SPE through better observations and research, consideration of HZE particles in real-time forecasting and monitoring, improved knowledge of the biological effects of the particles involved in SPE, and the development of methods for combining SPE forecasts with temporary shielding and chemical countermeasures. Evaluation of present capabilities and the identification of areas of further research to achieve the necessary capabilities are discussed.