Numerical simulation for diagnosis of thermospheric dynamics and composition

A numerical model of the thermosphere has been developed to study dynamical and compositional changes in response to auroral activity. High-latitude energy input associated with auroral activities are estimated by using empirical models of high-latitude ionosphere constructed from the two data bases: particle energy flux measured by the TIROS/NOAA satellites and ion drift velocity measured by the Millstone Hill incoherent scatter radar. This paper outlines these models of the thermosphere and ionosphere. In order to diagnose thermospheric dynamics and composition, it is important to investigate quantitatively their relationship to the auroral activities. From this point of view, the dynamical and compositional structure, being characteristic to a specified auroral activity level, has been simulated. Furthermore, a calculation has been done to simulate the transition of the neutral temperature between the two different activity levels. Some results of these simulations are discussed. (author)