Peculiarities of acoustic-gravity waves in inhomogeneous flows of the polar thermosphere

The peculiarities of acoustic-gravity waves propagating in inhomogeneous polar thermosphere flows have been investigated. It is shown that a spectrum filtration and a change in amplitudes of acoustic-gravity waves occur in the region of polar thermosphere circulation. As a result, the waves with horizontal lengths of 500-700 km and periods of ∼ 10 min are predominated in satellite observations. We have shown that such spectral properties correspond to the waves which are blocked in the counter flow. The amplitudes of the blocked waves are greatly enhanced due to their interaction with the non-uniform flow. A ground-based observer registers these waves with periods from 30 min to more than 1 h, depending on the flow velocity. Taking in to account the interaction of the waves with the flows we can explain the discrepancy between the results of satellite and ground-based observations of acoustic-gravity wave in the polar regions.