Dynamics of the thermosphere at high latitudes

In contrast with the low‐latitude thermosphere, which derives most of its energy from the absorption of solar extreme ultraviolet radiation (EUV), the energy balance of the high‐latitude thermosphere is dependent on processes of magnetospheric origin. Particles precipitating from the magnetosphere deposit energy in the lower thermosphere throughout the high‐latitude region. Processes such as magnetospheric convection drive bulk motions of charged particles; both energy and momentum are transferred to the neutral atmosphere by collisions between neutral constituents and these charged particles. The present paper presents a review of both observational and theoretical investigations of the response of the neutral upper atmosphere to processes which are unique to high latitudes. It also describes in some detail recent three‐dimensional model calculations dealing with the effects of magnetospheric convection on thermospheric dynamics. The three‐dimensional calculations, which treat the effects of viscosity, ion drag, the Coriolis force, thermal conduction, and solar EUV heating, as well as Joule and particle precipitation heating, allow an assessment of the relative importance of processes characteristic of high latitudes.