The Influence of the Inner Magnetospheric Electric Field on Plasma Sheet Access

Abstract

This study presents observations of the large-scale electric field and H⁺ fluxes over the entire Van Allen Probes mission duration. These observations are used to determine the spatial distributions of the azimuthal component of the ExB drift velocity and the plasma sheet H⁺ pressure, and their geomagnetic activity dependence. To investigate the influence of the inner magnetospheric electric field on H⁺ plasma sheet access, the boundary of zero azimuthal ExB drift velocity (BZEB) is identified as a proxy of the inner extent of the convection electric field and its characteristics are compared with that of the inner edge of the H⁺ plasma sheet (H⁺ IEPS). We find that the large-scale convection electric field has a dominant role on H⁺ plasma sheet access. This is evidenced by the good correlation between the BZEB and the H⁺ IEPS. Both boundaries present overall deeper access with increasing Kp. Moreover, both boundaries exhibit a similar deeper access on the evening sector compared to the afternoon sector, and both boundaries are more closely collocated in L for moderate and high Kp, while for low Kp the H⁺ IEPS is located at lower L than the BZEB. Furthermore, the collocation of both boundaries in L is better in the evening sector than in the afternoon sector, where the H⁺ IEPS lies farther inward in the afternoon sector for all Kp levels. This implies that the afternoon sector is the preferred region of the overlap between the hot ion plasma sheet and the cold plasmasphere.