Detailed Analysis of Electron Precipitation induced by ULF waves

Electron precipitation induced by ultralow frequency (ULF) wave directly has been proposed to be a potential mechanism for electron loss to the atmosphere and for the observed precipitation pattern in millihertz frequency range. In this study, we investigate the detailed precipitation process under ULF wave influence using the poloidal wave model and test particle simulation. By analysis from the view of electron bounce motion, the importance of azimuthal electric field is revealed that ULF induced precipitation would occur with westward electric field, with electrons conserving the first adiabatic invariant, rather than related to loss cone modulation by compressional magnetic component. Also, the energy dependence is shown that the precipitated electrons with lower energy would penetrate deeper in the loss cone than higher energy electrons and the typical difference between the local loss cone and pitch angle is provided under different wave intensities. Further, we simulated the time profile of electron precipitation and potential flux value with growing ULF modulation, and the result shows the longer duration of electrons with drift resonance energy. This study could enhance our understanding of electron precipitation induced by ULF wave and could be a comparison for potential observations from balloon or ground-based instruments.