Thermal plasmaspheric morphology: Effect of geomagnetic and solar activity

A multispecies kinetic model of the thermal plasma in the plasmasphere is u sed to predict the spatial dependence of the hydrogen ion and helium ion de nsity and temperature for different levels of geomagnetic and solar activit y. The particular convection electric held model chosen is intended for the time intervals between substorms. The plasma density and temperature in th e equatorial plane are found to exhibit a local-time variation that is sens itive to the details of the convection electric field. In particular, the p arallel temperature increases with altitude and the perpendicular temperatu re decreases with altitude, except in the postmidnight sector, features tha t are only possible if kinetic effects are taken into account. In addition, the ratio of the helium ion density to the hydrogen ion density is found t o agree with observations of the Dynamics Explorer 1 satellite. This behavi or can be explained by the effects of convection on the thermal particles t hat are magnetically trapped on closed field lines. These results have impl ications for the interpretation and analysis of sunlight scattered by heliu m ions (He II) to be measured by future global imaging satellites.