The formation of electron-temperature hot spots in the main ionospheric trough by the internal processes

Abstract

Abstract. A mathematical model of the convecting high-latitude ionosphere is described which produces three-dimensional distributions of electron density, positive-ion velocity and electron and ion temperatures at the F-layer altitudes. The results of simulation of the behaviour of the high-latitude ionosphere, in particular, the heat regime of the F-layer, are presented and analysed. From our study, it was found that electron-temperature hot spots in the main ionospheric trough can arise owing to internal ionospheric processes, and not due to effects of any external causes. Three conditions, to be satisfied simultaneously, are necessary for the formation of the considered electron-temperature hot spots: first, low values of electron density; second, solar illumination of the upper F region and darkness of the lower F region; third, low values of neutral-component densities. These conditions are valid in the main ionospheric trough near the terminator on the nightside when the density of the neutral atmosphere is not high. The physical processes which lead to the formation of the electron-temperature hot spots are the heat transfer from the upper into the lower F region, the reduced heat capacity of electron gas and the weakened cooling of electron gas due to inelastic collisions with neutral atoms and molecules. Also investigated is the influence of seasonal and solar-activity variations on the efficiency of the identified mechanism responsible for the formation of the electron temperature peaks in the main ionospheric trough by the internal processes.