Coupling of the Localized Wind Wall at High Latitudes to the Lower Thermosphere by Neutral Cells

Abstract

The recently observed Wall in the daytime zonal winds in the thermosphere from O (1S) and O (1D) emissions by the WINDII instrument on the UARS satellite in the high latitudinal region during 1994 to 1996, has been interpreted in terms of NCAR-TIGCM models. The strong westward polar wind (convergence) and weaker eastward winds equator wards of it (divergence), potentially generating localized vertical flows, overlap the dayside high density and equatorward of it low density neutral Cells’ regions in the models. The models indicate that the Cells and the Wall separating them exist at all solar and geomagnetic activities. These Cells in the thermosphere can transport neutral gas vertically down in the convergence region and up in the divergence region thus moving the associated emissions as observed in the data. Since the diameter of these Cells can reach up to 2000 km, the resulting enhanced emissions may have scale size of about 20° in latitude and longitude. The idealized transport time is under 8 minutes for up to 100 km for these observations during quiet solar and geomagnetic conditions. Once the transporting Cell’s temperature / density reaches that of the ambient atmosphere they disappear and other Cells will partake in this process at these latitudes and times.