A theoretical study of the distribution of ionization in the high-latitude ionosphere and the plasmasphere: first results on the mid-latitude trough and the light-ion trough

Abstract

A model of the O + and H + distributions in the plasmasphere and high-latitude ionosphere is described and first results are presented. The O + and H + continuity and momentum equations are solved from the F-region to the equatorial plane in the inner plasmasphere, and to an altitude of 1400 km in the outer plasmasphere and high-latitude ionosphere. Account is taken of high-latitude convection, departure from corotation inside the plasmasphere, and neutral air winds. The neutral air winds are consistent with the assumed convection pattern. For equinox and magnetically quiet conditions the calculations show that a mid-latitude trough in F-layer electron concentration is present from 1600 to 0600 LT and the trough may occur either inside or outside the plasmasphere. The movement of the trough in this period is from higher to lower latitudes and is in qualitative agreement with AE-C and ESRO-4 data. A light-ion trough feature is apparent in the H + distribution in the topside ionosphere at all local times. During the day the upward H + flow increases with latitude to produce the light-ion trough. At night the H + trough may be directly produced by the occurrence of the mid-latitude O + trough. The relationships between the position of the plasmapause and the trough are discussed. Also discussed are the influence of particle ionization in the auroral zone and the effect of the neutral air wind.