A comparison of thermospheric neutral gas heating and related thermal and energetic plasma phenomena at high latitudes during geomagnetic disturbances

Abstract

Simultaneous in situ measurements of energetic particle fluxes, ionospheric parameters, and neutral atmospheric parameters from the polar-orbiting satellite Esro 4 were made at altitudes in the range 250–500 km at middle and high latitudes. A study of changes in the parameters in both position and magnitude during geomagnetic disturbances in December 1972 and February 1973 showed three main regions of neutral atmosphere disturbance following the onset of magnetic activity indicated by the value of the Kp index. First, the largest effect was an enhancement of the N2 and Ar densities and reduction of the He density over the whole polar cap. Second, on the night side middle- to high-latitude region an enhancement of N2 density correlated with the zone of > 44-keV-electron flux was observed, and this N2 enhancement was correlated with the equatorward edge of the ionospheric plasma trough, the poleward edge of the latter being coincident with the equatorward edge of the 200-eV-electron flux zone. Third, on the day side a narrow region of enhanced N2 density was frequently observed at invariant latitudes of 70°–80°. This heating region generally coincided with a narrow plasma trough and a region of enhanced electron temperature.