The Origin and Propagation of Acoustic?Gravity Waves Ducted in the Thermosphere

Abstract

The theory of acoustic-gravity waves in a thermoclinal atmosphere shows that damping decreases as the thermal gradient increases. If the thermal gradient is large enough it offsets the increase in amplitude caused by upward propagation into a region of decreasing ambient density and the motion is completely undamped, neglecting viscosity. Thus it appears that long distance propagation can occur in the principal duct at 150 km altitude, where the thermal gradient is almost large enough to eliminate nonviscous damping.