A Simple Model of the Transient Response of the Thermosphere to Impulsive Forcing

Abstract

Abstract Substantial variations in density, temperature and winds in the high-latitude thermosphere during geomagnetic substorms have been recorded using a wide variety of observational techniques. The disturbed state of the thermosphere may be brought about by a sudden addition of heat or momentum. The heating may be due either to Joule heating or energetic particle precipitation, and the momentum source is due to the drag that neutrals feel when colliding with ions. We have studied dynamical adjustment of the disturbed high-latitude thermosphere toward geostrophic equilibrium using an idealized high-resolution time-dependent scale model that includes the effects of the earth's rotation. The model describes the response of a compressible stratified atmosphere to horizontally and vertically extended sources. Our results show that the effect of rotation depends strongly upon the type and vertical scale of the forcing. In the ion-drag case, the pressure gradients that are required to maintain steady balance...