ACOUSTIC-GRAVITY WAVE GROWTH AND DAMPING IN CONVECTING PLASMA

The propagation of acoustic gravity waves through steadily convecting plasma in the thermosphere has been analysed theoretically, The growth and damping rates of internal gravity waves due to the feedback effec ts of wave-modulated Joule heating and Laplace forcing have been calcu lated. It is found that large convection flow velocities lead to the g rowth of large-scale internal gravity waves, whilst small- and medium- scale waves are heavily damped, under similar conditions. It has also been shown that wave growth is favoured for waves travelling against t he plasma flow direction. The effects of critical coupling when wave p hase speeds match the plasma flow speed have also been investigated. T he results of these calculations are discussed in the context of the a tmospheric energy budget and thermosphere-ionosphere coupling.