Effects of Internal Gravity Waves in the Thermosphere Above the Turbopause

We present results of the study of gravity wave (GW) effects on the circulation in the thermosphere-ionosphere (TI). A spectral GW drag scheme suitable for the thermosphere has been developed and implemented into the Coupled Middle Atmosphere-Thermosphere Model (CMAT2) extending from the lower atmosphere into the F- region. Results of the simulations demonstrate that GWs of the tropospheric origin can effectively penetrate into the upper thermosphere. Momentum deposited by these waves is not only negligible above the turbopause, but is comparable to that of ion drag, at least up to 180-200 km. Effects of the thermospheric GW drag are particularly noticeable in the winter hemisphere, where the inclusion of GW parameterization allowed to reproduce weaker westerlies and stronger high-latitude easterlies, well in agreement with the empirical Horizontal Wind Model. We shall discuss some inferences concerning the dynamic response in the F-region to the variations of the source spectrum.