5. Conclusions
In this study, based on the high-resolution proton flux data from RBSPICE onboard the Van Allen Probe B during 2013 – 2016, we have performed a detailed statistical analysis of the global distribution of reversed energy spectra of ring current protons. The major conclusions are summarized as follows:
(1) The reversed proton energy spectra are preferentially observed inside the plasmasphere, with the occurrence rates > 90% at L ~ 2 - 4 during geomagnetically quiet periods. As the geomagnetic activity intensifies, the preferential occurrence region of the reversed proton energy spectra shrinks to lower L shells (~2.5 - 3.5).
(2) The proton energies corresponding to the flux maxima and minima of the reversed energy spectra decrease with the increase of L shell in the region of L < 5. The flux minima of the reversed proton spectra mainly occur at ~50 - 100 keV, while the flux maxima are generally present at ~200 - 400 keV.
(3) Similar to the global distribution of the reversed spectrum occurrence rate, the ratios between flux maxima and minima are strongly L shell and geomagnetic activity dependent, showing that the ratios during active times and at higher L shells are smaller than those during quiet times and at lower L shells.