Spectral distributions of electron phase space density in the Earth's radiation belt.

This article focuses on the classification and dynamics of Earth's radiation belt electron phase space density (PSD) spectra, analyzed using Van Allen Probe-B data from 2012 to 2019. It identifies three main PSD spectral types—exponential, power law, and bump-on-tail (BOT)—distributed differently relative to the plasmapause location (Lpp): power law spectra dominate outside the plasmasphere and can penetrate inward after strong geomagnetic storms, BOT spectra prevail near the inner outer belt and slot region during quiet geomagnetic periods, and exponential spectra appear as intermediates near Lpp. The study highlights that geomagnetic activity, solar wind dynamic pressure, and wave–particle interactions, including whistler-mode chorus and plasmaspheric hiss waves, play key roles in shaping these spectral distributions and their temporal evolution.