Variations of hot O in the thermosphere

Using measurements of electron temperature and density, a model of neutral density, and a theoretical expression for the O+-O collision cross section, we compute the ion temperature and find it to be lower than the measured v alue. We compute the amount of hot O at 4000 degrees K necessary to provide this heat deficit. At 400 km altitude very little hot O is needed at solar maximum while 1-2% of total O must be hot at solar maximum. Hot O densitie s at 400 km altitude are lowest during the day, highest at night; lowest at the equinoxes, highest at the solstices; lowest at solar maximum, highest at solar minimum, lowest for magnetically disturbed periods, highest for qu iet periods; lowest for a warm, dense thermosphere, highest for a cool, rar e thermosphere. All of these variations are consistent with thermal quenchi ng by ambient O, with larger ambient O densities yielding lower hot O densi ties. This indicates that hot O should form a layer shape in the atmosphere .