Substorm influences on plasma properties distributions in the inner magnetosphere

The plasma properties in the inner magnetosphere play critical roles in plasma dynamics by changing magnetic field configurations and generating the ring current. Geomagnetic substorms, especially intense substorms can significantly influence inner magnetosphere. This study presents our preliminary statistical results of plasma properties and their substorm dependence at the equatorial plane based on the Van Allen Probe observations. We find that both H+ and O+ pressure increases significantly during substorms, and the pressure ratio of O+ to H+ also increases. The peak of H+ pressure is almost fixed around L=4, while that of O+ moves inward as the substorm intensifies. In addition, substorms can significantly change the ion energy distributions. They will increase the proportion of pressure provided by the lower energy components of H+ (E < ~100keV), especially in lower L-shells. At the same time, they decrease the contribution to the plasma pressure from lower energy components of O+, which shows almost no L-shell dependence. During quiet times, the perpendicular current density distributes roughly symmetrically, with negative value inside (L < ~4.5) and positive value outside. During substorms, the current density enhances and shows asymmetry with higher current density from the pre-dusk to the post-midnight. The parallel current density caused by the pressure gradient also increases with substorms. These field-aligned currents (FACs) enter the ionosphere at dusk and move upward at dawn, as region II FAC.