Characteristics of Electron Precipitation Directly Driven by Poloidal ULF Waves

A mechanism recently proposed for magnetospheric electron loss into the atmosphere is the precipitation directly driven by ultralow-frequency (ULF) waves. In this study, we quantitatively analyze the properties of ULF wave-induced precipitation by simulating the electron bounce and drift motion in poloidal-mode waves excited in a dipole magnetic field. Our results reveal that precipitation occurs only when electrons encounter a westward-directed wave electric field in the magnetosphere, which leads to cross-field energy enhancements and reduces their mirror heights. The simulations also demonstrate longer duration electron precipitation at the drift-resonance energy. We calculate the temporal variations of the energy spectrum for precipitating electrons and the total precipitating energy fluxes. These results improve our understanding of ULF wave-induced electron precipitation as well as provide a point of comparison for observations from balloons or ground-based instruments.