Electron Backscatter in Energetic Particle Precipitation: Data Analysis and Simulation

Abstract When particles from the radiation belts impinge on the atmosphere, they can be absorbed into the atmosphere or deflected back into the magnetosphere. The deflection of particles back into the magnetosphere is known as backscatter, and it is a key link connecting the atmosphere to the magnetosphere—involving collisions with atmospheric neutrals, magnetic mirroring, the production of secondary emissions, and energy transfer from the particle to the atmosphere. Backscatter is both a feedback mechanism to magnetospheric precipitation drivers and an indirect measure of atmospheric energy absorption, making it an important process to quantify and understand. In this work, we use data from the Electron Fields and Losses INvestigation (ELFIN) satellites to quantify backscatter rates. We find that backscatter rates vary between during periods of loss cone filling and during periods without loss cone filling. We then compare the ELFIN backscatter data to the results of an updated and improved Monte Carlo‐based simulation and find excellent agreement with ELFIN‐measured backscatter rates. Finally, we use our improved Monte Carlo model to characterize the pitch angle and energy dependence of backscatter and the pitch angle distributions of backscattered electrons, finding results consistent with previous modeling efforts.