Radiation belt energetic particle precipitation analysis using RBSP and SAMPEX

Abstract:

Wave particle interactions are an important precipitation mechanism in the outer radiation belts. In order to better understand their effect on the radiation belts and to explore the connection between precipitation and its drivers, we study relativistic electrons with the Van Allen Probes and the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX). SAMPEX, a low Earth orbiting satellite, measured relativistic electron microbursts for over two solar cycles before it re-entered the Earth’s atmosphere. We study the relationship between relativistic microbursts with energies >1MeV and global flux decay of electrons from the outer Van Allen belt during the recovery phase of storms. Our studies show that microbursts are effective at emptying the radiation belts on the scale of days. We also show the distribution of microburst precipitation in relation to the plasmapause. We report on a study that examines the connection between pitch angle distribution evolution and electron precipitation, and their driver-dependence (CME vs. CIR) using energetic electron data from the REPT sensor onboard the Van Allen Probes. Our results show that, consistently across all storms with ultra relativistic electron energization, electrons become most anisotropic within around a day of Dst minimum and slowly relax down to prestorm isotropization levels in the following week. Using a superposed epoch analysis, we show that the peak anisotropies differ between CME- and CIR- driven storms and measure the relaxation rate as the anisotropy falls after the storm.