NONLINEAR UNSTABLE AURORAL-ARC DRIVEN THERMOSPHERIC WINDS IN AN IONOSPHERE-MAGNETOSPHERE COUPLED MODEL

The nonlinear evolution of thermospheric winds in an ionosphere-magnet osphere coupled model has been studied for the first time for, a dynam ic unstable auroral-arc environment. We treat the problem using a mult i-layer, quasi-three-dimensional model which averages in altitude the thermospheric dynamics over each layer. For the upper thermosphere, we find that (1) the thermosphere can respond to the ionospheric Kelvin- Helmholtz (KH) instability on temporal scales on the order of an hour, depending on ambient conditions, and on spatial scales of tens to hun dreds of kilometers, (2) strong thermospheric meridional and zonal vor tical flows with embedded nonlinear jet-like structures can be generat ed by the ionospheric/magnetospheric KH instability and (3) neutral th ermospheric winds, vortices, and associated power spectra develop in a distinctly different manner in the presence of magnetospheric couplin g effects. Comparison with recent observations is made.