Global distribution of reversed energy spectra of ring current protons
based on Van Allen Probes observations
Abstract
Energy spectra of ring current protons are crucial to understanding the
ring current dynamics. Based on high-quality Van Allen Probes RBSPICE
measurements, we investigate the global distribution of the reversed
proton energy spectra using the 2013-2016 RBSPICE datasets. The reversed
proton energy spectra are characterized by the distinct flux minima
around 50 - 100 keV and flux maxima around 200 - 400 keV. Our results
show that the reversed proton energy spectrum is prevalent inside the
plasmasphere, with the occurrence rates > 90% at L
~ 2 - 4 during geomagnetically quiet periods. Its
occurrence also manifests a significant decrease trend with increasing
L-shell and enhanced geomagnetic activity. It is indicated that the
substorm-associated processes are likely to lead to the disappearances
of the reversed spectra. These results provide important clues for
exploring the underlying physical mechanisms responsible for the
formation and evolution of reversed proton energy spectra.