BACKGROUND WIND INFLUENCE ON THE FORMATIO N OF ACOUSTIC-GRAVITY WAVESVERTICAL STRUCTURE IN THE THERMOSPHERE

A numerical model for simulation of acoustic-gravity waves (AGW) in th e middle and upper atmosphere, taking into consideration the molecular dissipation and background temperature and wind profiles, is develope d. AGW vertical structure is calculated for the parameters that are ty pical for medium-scale traveling ionospheric disturbances. The results show that background wind strongly influences the efficiency of AGW t ransformation into thermal conduction and viscous waves at the heights of the transition region, where the dissipation begins to play a subs tantial role. Through its effects on the waves propagation, background wind in the transition region may create or remove the conditions of the waves penetration into the upper thermosphere. A conclusion is mad e that observed in the real thermosphere anizothropy of propagation di rections for AGW with phase velocities similar to 100 m/s may be accou nted for through the joint consideration of the background wind and mo lecular dissipation effects.