The Effect of Ring Current Heating on Plasmaspheric Ion Composition: Explaining the O+ Torus

Abstract:

A localized, cold O+ enhancement, commonly referred to as the O+ torus, has been routinely observed in the inner magnetosphere. The mechanism that produces this feature, however, is still not well understood. One suggested mechanism involves interactions between the ring current and the plasmasphere resulting in a transfer of energy between these populations through either Coulomb collisions or wave-particle interactions. Ultimately, the heat gained by the thermal plasma is conducted into the topside ionosphere where it raises the plasma temperatures. This increases the scale height of O+ in the topside ionosphere, resulting in an increase of the O+ mass loading into the inner magnetosphere. To investigate the impact of this process on the plasmaspheric O+ density and the extent to which it can explain observed O+ enhancements, we use the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model to quantify the ring current heating due to Coulomb collisions and the Ionosphere-Plasmasphere-Electrodynamics model (IPE) to evaluate the impact of this heating on ionospheric plasma temperatures and the resulting plasmaspheric composition. The results will be evaluated against incoherent scatter radar, low earth orbiting satellites platforms (DMSP) and inner magnetospheric measurements.