Ring current-plasmasphere coupling through Coulomb collisions

Abstract

In the ring current-plasmasphere region, two plasma populations interact with each other via multiple processes, such as Coulomb collisions and waveparticle interactions. In this paper, the consequences of coupling between ring current ions and the plasmasphere through Coulomb collisions are examined. A kinetic Ring Current-Atmosphere Interaction Model (RAM) has been used to solve the temporal evolution of the ring current ion distribution and obtain the instantaneous ring current heating to the plasmasphere through Coulomb collisions. A buildup of low-energy (< 1 keV) ion population is found as a result of energy degradation of ring current ions in a background of thermal plasma. The drift-holes in the ring current ion energy spectra are also somewhat smoothed out by Coulomb interactions. Energy transferred from ring current ions to the plasmasphere is a source of plasma heating and results in enhanced plasma temperatures at high altitudes. The ion temperatures calculated from the FLIP (Field Line Interhemispheric Plasma) model, taking into account the additional heat source from the ring current, appear to be consistent with the enhanced ion temperatures observed in the high altitude regime.