Effects of thermospheric gravity waves on the polar ionosphere

One of the results of the European, United States, and Japanese efforts to establish extensive polar cap observational facilities will be the generation of simultaneous and complementary two-dimensional ionosphere and thermosphere data bases. In anticipation of these extensive data sets, this paper considers the coupling between the thermosphere and ionosphere in the polar region from a theoretical point of view, aided by the USU Time Dependent Ionospheric Model (TDIM). To date, we have used statistical climatology thermospheric drivers; these being the Hedin neutral atmosphere (MSIS) and neutral wind models (Hedin et al., 1991). These inputs do not contain gravity waves. The question of prime interest in this paper is: What will a gravity wave do to the high-latitude ionosphere and can these new data sets capture enough of the two-dimensional time evolution of the phenomenon to unambiguously identify the perturbations? Our modeling results indicate that an antisunward propagating gravity wave with a phase velocity that is the same as the plasma convection velocity will experience a constant vertical force from the thermosphere, which amplifies the effect of the gravity wave. ©1998 COSPAR. Published by Elsevier Science Ltd.