Relative flow of H + and O + ions in the topside ionosphere at mid-latitudes

Abstract

Theoretical results on the daily variation of O + and H + field-aligned velocities in the topside ionosphere are presented. The results are for an L = 3 magnetic field tube under sunspot minimum conditions at equinox. They come from calculations of time-dependent O + and H + continuity and momentum balance in a magnetic field tube which extends from the lower F2 region to the equatorial plane (Murphy et al., 1976). There are occasions when ion counterstreaming occurs, with the O + velocity upward and H + velocity downward. The conditions causing this counterstreaming are described: the H + layer is descending whilst O + is supplied from below either to increase the O + concentration at fixed heights or to replace O + ions lost by charge exchange with neutral H. It is suggested that the results of observations at Arecibo by Vickrey et al. (1976) of O + and H + concentrations and counterstreaming velocities are significantly affected by E × B drift.