Thermospheric dynamics during November 21–22, 1981: Dynamics Explorer measurements and thermospheric general circulation model predictions

Abstract

Time‐dependent aurora and magnetospheric convection parameterizations have been derived from solar wind and aurora particle data for November 21–22, 1981. These parameterizations are used to drive the auroral and magnetospheric convection models that are embedded in the National Center for Atmospheric Research thermospheric general circulation model (TGCM). The TGCM has been used to calculate the time‐dependent global circulation, temperature and compositional structures for the geomagnetic moderately disturbed period. The results of the TGCM calculation are compared with measurements made by the Dynamics Explorer 2 satellite along its orbital path during several passes over the northern and southern hemisphere polar caps. TGCM input parameterizations of auroral particle precipitation and ion drift generally agree with satellite measurements of these inputs for the period. There is also good agreement between TGCM‐predicted neutral winds and DE 2 neutral wind observations showing the dominant influence of magnetospheric convection on the high‐latitude circulation. On the eveningside of the auroral oval there is a transition from a magnetospheric convection‐driven wind pattern at high magnetic latitudes to one that is driven principally by solar EUV and UV heating at middle and low latitudes. This transition is consistent with the measured latitudinal falloff of electric field strength. The comparison of experimental measurements and time‐dependent model calculations demonstrates that the great natural variability that is observed in the large‐scale structure and dynamics in the thermosphere can be interpreted successfully in terms of variations in the thermospheric forcing mechanisms that are incorporated in the TGCM.