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radiation belts; multi‐MeV electrons; EMIC waves
Abstract:
During geomagnetic storms, the rapid depletion of the high‐energy (several MeV) outer radiation belt electrons is the result of loss to the interplanetary medium through the magnetopause, outward radial diffusion, and loss to the atmosphere due to wave‐particle interactions. We have performed a statistical study of 110 storms using pitch angle resolved electron flux measurements from the Van Allen Probes mission and found that inside of the radiation belt (L * = 3 − 5) the number of storms that result in depletion of electrons with equatorial pitch angle α eq = 30∘ is higher than number of storms that result in depletion of electrons with equatorial pitch angle α eq = 75∘. We conclude that this result is consistent with electron scattering by whistler and electromagnetic ion cyclotron waves. At the outer edge of the radiation belt (L * ≥ 5.2) the number of storms that result in depletion is also large (~40–50%), emphasizing the significance of the magnetopause shadowing effect and outward radial transport.
Abstract:
Plain Language Summary: Protons and electrons form a radiation environment around Earth that can change drastically during so called geomagnetic storms . In this study, we looked at 110 storms to understand how high‐energy electrons can disappear due to different phenomena. We found that it is very common to observe a loss of high‐energy electrons after storms. More often such a loss happens far away from the Earth as the electrons cross the boundary of the magnetosphere. However, closer to Earth the electrons are lost most likely due to the interaction with whistler and electromagnetic ion cyclotron waves , which play an important role in the dynamics of the radiation environment.
