The Ring Current Plasma Pressure: The Roles of the Electric Field and Charge Exchange Losses

The terrestrial ring current is an electric current flowing around the Earth at geocentric distances of 2-8 Earth radii (RE). Variations in the ring current are responsible for global decreases in the magnetic field at the surface of the Earth, which constitute the signature of geomagnetic storms. The ring current flow is mainly westward and carried by ions with energies in the range of 10s to 100s of keV. Furthermore, it is one of the main plasma populations in the inner magnetosphere, carrying most of the plasma pressure, as transport of the nightside plasma sheet deep into the inner magnetosphere gives rise to the ring current development.
In this presentation, we use flux measurements from NASA’s Van Allen Probes mission, spanning the entire duration of the mission, to calculate the particle pressures for the four main magnetospheric particle species, e-, H+, He+, and O+. Using the particle pressures, we investigate their statistical distributions and energy and geomagnetic activity dependence. We also discuss the roles that the electric field and losses due to charge exchange interactions play in determining the ring current plasma pressure dynamics.