September 28, 2022

The flux intensity of energetic electrons in Earth's outer radiation belt is due to a delicate imbalance between transport, acceleration, and losses. Wave-particle interactions contribute critically to all three of these competing processes. Chief amongst them are ULF wave-related transport, whistler-mode chorus associated acceleration, and EMIC or hiss wave related losses. Although a combination of these interactions can explain the evolution of energetic electron fluxes over long timescales (tens of hours to days), rapid electron flux variations cannot always be explained by them. One important discrepancy is the rapid dropout of 0.1-1 MeV electrons. These energies are too low to be scattered by resonant interactions with EMIC waves, whereas the dropout timescale is too short to be explained by the scattering rates from whistler-mode hiss waves. One possible candidate is the scattering by Kinetic Alfven waves (KAW) that can potentially resonate with these high-energy electrons and scatter them into the loss cone, but contribution of this wave mode to radiation belt dynamics has not been thoroughly studied.

The primary goal of this project is to improve our understanding on mechanisms of energetic electron losses in the inner magnetosphere (including radiation belts) by quantifying the KAW contribution to energetic electron scattering in the radiation belts. Key proposal objectives are: (i) to explore direct evidence of KAW resulted electron precipitation, using combined near-equatorial and low-altitude observations by near-equatorial NASA missions (THEMIS, MMS, and Van Allen Probes) and observations of precipitating energetic electrons by ELFIN (low-altitude twin CubeSat mission). (ii) Verify the KAW diffusion rates by comparing the expected and observed precipitating electron fluxes in multiple conjunction events.