Azimuthal hot plasma pressure gradients and dawn-dusk electric field formation

Abstract

Abstract The effects of hot plasma pressure gradients in the high latitude magnetosphere are analysed. It is shown that such a mechanism may in fact be responsible for Region 1 field-aligned currents and for the dawn-dusk electric field. The estimated azimuthal gradients in the plasma pressure may account for the observed field-aligned currents and also give the opportunity to determine the day-night plasma pressure changes along isosurfaces of magnetic flux tube volume. These pressure changes are then compared with experimentally measured pressure distribution and it is shown that the day-night plasma change, in the high latitude magnetosphere, may be high enough to sustain Region 1 currents. The closure of these currents in the high latitude magnetosphere may in turn be responsible for the dawn-dusk electric field and the dawn-dusk potential drop in the inner plasma sheet regions. The influence of the IMF on the magnetostatically equilibrium inner magnetospheric currents may qualitatively explain the IMF control of the dawn-dusk electric field and magnetospheric activity.