Multi‐instrument Observation of Nonlinear EMIC‐Driven Electron Precipitation at sub–MeV Energies

Abstract

AbstractIn recent years, experimental results have consistently shown evidence of electromagnetic ion cyclotron (EMIC) wave‐driven electron precipitation down to energies as low as hundreds of keV. However, this is at odds with the limits expected from quasi‐linear theory. Recent analysis using nonlinear theory has suggested energy limits as low as hundreds of keV, consistent with the experimental results, although to date this has not been experimentally verified. In this study, we present concurrent observations from Polar‐orbiting Operational Environmental Satellite, Radiation Belt Storm Probes, Global Positioning System, and ground‐based instruments, showing concurrent EMIC waves and sub–MeV electron precipitation, and a global dropout in electron flux. We show through test particle simulation that the observed waves are capable of scattering electrons as low as hundreds of keV into the loss cone through nonlinear trapping, consistent with the experimentally observed electron precipitation.