Van Allen Probes based investigation of storm time enhancements in the duskward electric field to lower L shells and its effect on ring current formation and plasmasphere erosion.

The large scale convection electric field plays a central role in the dynamics of the inner magnetosphere; among which processes are ring current particle injection and plasmasphere erosion. Both of these are important for radiation belt dynamics. The ring current affects magnetic field geometry which in turn affects particle drift paths and plasmasphere erosion shrinks the region characterized by plasmaspheric hiss which would otherwise be present to scatter population of radiation belt seed electrons. Using the Van Allen Probes we investigate enhancements in the duskward electric field to lower L shells (L < 4 RE) and its role in ring current particle energization and erosion of the plasmasphere during two major storms; June 1, 2013 and February 19, 2014. During these storms, the electric field enhanced to low L shells with magnitudes ~1-2 mV/m in the co-rotating frame. The corresponding storm time ring current enhancements and plasmasphere erosions are examined in the context of these electric fields. The intensification in the duskward electric field is of long enough duration to transport particles from locations characteristic of the earthward edge of the plasma sheet (L shells ~ 8-10 RE) to the observed location of the ring current while energizing them though conservation of the first adiabatic invariant to energies typical of the ring current. It is also observed that the range in L shell over which the most intense nightside, duskward, electric field is observed is also that over which the higher pressure region of the ring current is located.