Work

Including Atmospheric Backscatter Effects in Modeling of EMIC Wave‐Driven Precipitation

Year: 2025

Type: article

Abstract: Pitch‐angle diffusion is a key mechanism driving radiation belt electron loss into the atmosphere. However, traditional bounce‐averaged models, which assume complete atmospheric absorption for loss cone electrons, cannot accurately quantify the loss cone fluxes. This shortfall arises primarily from two issues: bounce‐averaging assumptions generally breakdown within the loss cone, and atmospheric backscatter effects are omitted. In this study, we use a modified bounce‐averaged pitch‐angle diffusion model to show that the inclusion of backscatter effects inside the loss cone can adequately estimate the pitch‐angle distribution of electrons inside the loss cone for the case of Electromagnetic Ion Cyclotron (EMIC) wave‐driven precipitation. In this modified model, atmospheric backscatter effects are incorporated as an additional backscatter‐induced pitch‐angle diffusion (), and an attenuation of atmospheric absorption (). Here, we quantify the values of and using Geant4‐based Monte Carlo atmospheric backscatter simulation and applied to model electron precipitation driven by EMIC waves. Comparisons with ELFIN satellite observations during EMIC events reveal that the inclusion of atmospheric backscatter resolves previously reported discrepancies at electron energies . For electrons, where EMIC wave diffusion is dominant over backscatter‐induced diffusion, backscatter effects become negligible. Notably, we find that accounts for nearly all the observed enhancements in the loss cone flux, while plays a secondary role.

Source: Journal of Geophysical Research Space Physics

DOI: 10.1029/2025ja034333

Authors: Zhi‐Gu Li, Weichao Tu, Richard Selesnick, Luisa Capannolo, Grant Berland, Qianli Ma