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

A mathematical model of the convectinghigh-latitude ionosphere is described which produces three-dimensionaldistributions of electron density, positive-ion velocity and electron and iontemperatures at the F-layer altitudes. The results of simulation of thebehaviour of the high-latitude ionosphere, in particular, the heat regime of theF-layer, are presented and analysed. From our study, it was found thatelectron-temperature hot spots in the main ionospheric trough can arise owing tointernal ionospheric processes, and not due to effects of any external causes.Three conditions, to be satisfied simultaneously, are necessary for theformation of the considered electron-temperature hot spots: first, low values ofelectron density; second, solar illumination of the upper F region and darknessof the lower F region; third, low values of neutral-component densities. Theseconditions are valid in the main ionospheric trough near the terminator on thenightside when the density of the neutral atmosphere is not high. The physicalprocesses which lead to the formation of the electron-temperature hot spots arethe heat transfer from the upper into the lower F region, the reduced heatcapacity of electron gas and the weakened cooling of electron gas due toinelastic collisions with neutral atoms and molecules. Also investigated is theinfluence of seasonal and solar-activity variations on the efficiency of theidentified mechanism responsible for the formation of the electron temperaturepeaks in the main ionospheric trough by the internal processes