Van Allen Probes Survey of the Plasmasphere and the Inner Magnetosphere Electric Field

Abstract We present a statistical study of the convection electric field and cold plasma density in the inner magnetosphere for different levels of geomagnetic activity over the Van Allen Probes mission. In addition to presenting the average dawn‐to‐dusk component of the electric field, the electric field is also presented in radial and azimuthal components. The statistical state of the plasmasphere is presented and put into the context of the electric field. In the frame corotating with the Earth, a trail of radially outward electric field wraps around from the dusk side regions of strong electric field through the nightside to the dawn side. This electric field feature corresponds to a westward plasma drift. Outside this region of radially outward electric field, in the post‐midnight sector, there is a sharp reversal of the radial electric field to an inward orientation. This feature corresponds to a flow shear in the Earth corotating frame and we suggest it is the Harang discontinuity mapped into the equatorial plane. In the post‐noon sector, the enhanced dawn‐dusk electric field is associated with a significant electric field azimuthal component. This is consistent with the radially outward flow of plasma in the drainage plume. When mapped into the ionosphere, this electric field should be able to lift the F‐region plasma to higher altitudes, where the recombination rate is lower, enhancing density and consequentially increasing the outflow rate. This mechanism could be by directly adding plasma to the plume without having to first journey through the plasmasphere.