The behaviour of H + and He + ions in the topside ionosphere during a short-lived subauroral ion drift

Abstract

A model of the ionosphere and plasmasphere is used to investigate the effects of an imposed westward plasma drift on H + and He + behaviour in the nightside topside ionosphere. A closed subauroral tube of plasma is considered and the velocity spike, of maximum value 2 km s −1, persists for 10 min. The upward surge of O + flow (caused by frictional heating of the ions in the F-region) gives rise to rapid upward H + and He + flows. The H + and He + velocities in the topside are comparable to those of O + but the transient H + and He + fluxes are not significant contributors to the magnetospheric light ion population. Above 500 km altitude the ionospheric H + and He + densities decrease during the westward plasma drift.