Impact of Background Magnetic Field for EMIC Wave‐Driven Electron Precipitation

Abstract

AbstractWave‐particle interaction between relativistic electrons and electromagnetic ion cyclotron (EMIC) waves is a highly debated loss process contributing to the dynamics of Earth's radiation belts. Theoretical studies show that EMIC waves can result in strong loss of relativistic electrons in the radiation belts (Summers & Thorne, 2003, https://doi.org/10.1029/2002JA009489). However, many of these studies have not been validated by observations. Li et al. (2014, https://doi.org/10.1002/2014GL062273) modeled the relativistic electron precipitation observed by Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) in a single‐event case study based on a quasi‐linear diffusion model and observations by Van Allen Probes and GOES 13. We expand upon that study to investigate the localization of the precipitation region and the effectiveness of EMIC waves as an electron loss mechanism.The model results of BARREL 1I observations on 17 January 2013 show that as the BARREL balloon drifts in local time to regions that map to lower equatorial magnetic field strength, the flux of precipitating electrons increases and peaks at lower energy. The hypothesis that the energy of the precipitating electrons is controlled by background magnetic field strength is further tested by considering observations from balloon campaigns conducted from 2000 to 2014, including BARREL. Consistent with theory for wave‐particle interaction between relativistic electrons and EMIC waves, we find observationally that stronger equatorial magnetic field strength generally correlates with more energetic electron precipitation and further conclude that magnetic field strength can drive the localization and distribution of precipitating electrons.