Developing the Models of Acoustic-Gravity Waves in the Upper Atmosphere (Review)

The results of the authors’ studies of acoustic-gravity waves (AGW) in the upper Earth’s atmosphere for recent years are presented. The work was generally aimed at the development of theoretical AGW models taking into account the real atmosphere properties and the verification of these models by spacecraft measurement data. The possibility of the existence of new evanescent acoustic-gravity wave types was theoretically shown; in particular, a previously unknown inelastic mode and a family of evanescent pseudo-modes were revealed. The possibility of observing evanescent modes on the Sun and in the Earth’s atmosphere was analyzed. The specific features of the propagation of acoustic-gravity waves at the interface between two isothermal half-spaces with different temperatures depending on their spectral parameters and the temperature jump magnitude at the interface were studied. The peculiarities of the interaction of acoustic-gravity waves with spatially inhomogeneous atmospheric flows were also investigated. The observed effects resulting from such interaction were analyzed to reveal the wave propagation azimuths, the change in their amplitudes, and the effect of blocking in the counterflow. The effect of vertical nonisothermicity on the propagation of acoustic-gravity waves, including the modification of acoustic and gravitational regions depending on the temperature, was studied. Based on the modified Navier-Stokes and heat-transfer equations, the effect of attenuation on the propagation of acoustic-gravity waves in the atmosphere was analyzed. The specific features of the viscous attenuation of different evanescent AGW types in the atmosphere were considered. The rotation of the atmosphere was shown to result in the modification of the continuous spectrum of evanescent AGWs with frequencies exceeding the Coriolis parameter.