VERTICAL STRUCTURE OF AGW ASSOCIATED IONOSPHERIC FLUCTUATIONS IN THE E-REGION AND LOWER F-REGION OBSERVED WITH EISCAT - A CASE-STUDY

The vertical structure of AGW (atmospheric gravity wave) associated fluctuations of ionospheric plasma parameters for the 100-240 km altitude range in the daytime of 7 September 1988 has been investigated by making use of the data provided by the Tromso measurements in the EISCAT CP1 observation mode. The wave power profile vs height has been studied by integrating the power spectral density in each altitude. The essential feature of the power variation can be explained in terms of the energy conservation of AGWs propagating in a dissipative thermosphere. Intrinsic propagation parameters of the dominant AGW have been successfully estimated with a method based on the retrieval of the Doppler effect due to the horizontal prevailing wind. From the fluctuation structure analysis in a time-altitude frame, a downcoming AGW has been clearly identified. This downcoming wave might have been reflected from a wind shear at the altitude around 200 km, which is inferred from the meridional prevailing wind profile.