Radiation and Plasma Hazards to Satellites in the Declining Solar Cycle (Invited Presentation)

Solar maximum is characterized by sunspots, active regions, and eruptions, and the coronal mass ejections, solar energetic particle events and large magnetic storms that follow. The declining phase of the solar cycle typically sees a winding down of these CMEs and large magnetic storms. However, the coronal holes common to the declining phase produce routine, persistent, and recurrent high-speed streams which lead to space weather patterns at Earth that can be as hazardous to satellites as the eruptive transients. Long periods of elevated solar wind speed can lead to extreme conditions in the magnetically trapped MeV electron belts, which, in turn, increases the risk of internal charging on satellites. Fluctuations of the interplanetary magnetic field embedded in these high-speed streams drives auroral, substorm, and convection activity that bathes satellites in hot electron plasma capable of charging surfaces. Whereas the peak of the sunspot cycle typically sees enhanced single event effect and event total dose hazards to satellites, during the declining phase the dominant hazard is more often vehicle charging. This talk will illustrate these points through synoptic data sets with extreme cases identified.