A THEORETICAL INVESTIGATION OF SOURCES OF LARGE AND MEDIUM-SCALE ATMOSPHERIC GRAVITY-WAVES IN THE AURORAL OVAL

Many papers have been published to devise models to describe the sourc es of large and medium scale atmospheric gravity waves (AGWs) in the a uroral oval ionosphere. One of the models proposed by CHIMONAS and HIN ES [(1970) Planet. Space Sci. 18, 565] calculated the relative importa nce of Lorentz force and Joule heating as sources of AGWs in the auror al regions based on certain assumptions. In this paper, we develop a g eneral theory to describe the behavior of the AGW source terms. It has been found that the source terms which generate AGWs are closely rela ted to the velocities and frequencies of AGWs, and that the Lorentz fo rce is dominant in generating the vertical velocity perturbation of la rge scale AGWs. The formulas which determine the source term contribut ions are derived. This relationship gives us the possibility to predic t what kind of AGW will be generated by observing the source terms, or conversely perhaps to deduce some of the source characteristics by me asuring properties of the traveling ionospheric disturbances (TIDs).