Energetic magnetospheric protons in the plasma depletion layer

The characteristics of energetic protons (between a few keV/e and about 100 keV/e) leaked from the magnetosphere were determined using observations for 13 plasma depletion layer events recorded by AMPTE/CCE. Results indicate that, when the IMF has orientation such that the angle between the IMF and the X(GSE) direction is 60 deg (the condition under which the energetic ion regions upstream and downstream from the quasi-parallel bow shock are located on the flanks of the dawnside bow shock), the magnetospheric leakage provides only about 10 percent of the energetic proton distribution in the energy range from a few keV/e to 100 keV/e in the region upstream from the earth's bow shock. The other 90 percent come from the bow shock accelerated source.