THE TEMPERATURE ABOVE THE THERMOPAUSE,
Abstract:
The conversion of upper-atmosphere densities to temperatures by means of atmospheric models, whether time-dependent or static, is subject to limitations, which are critically examined. Nicolets model is used to obtain temperatures from the drag of five artificial satellites in the time interval from 1958 to 1963. The temperature variations with solar and geomagnetic activity are reviewed. The relation between the day and night temperatures averaged over one solar rotation and the corresponding decimetric solar flux shows a definite departure from linearity, which is just about the same for the 8 cm and the 10.7 cm flux. The diurnal variation is a very stable feature its 2 PM maximum and 4 AM minimum do not show any appreciable shift with solar activity, nor does the ratio of the maximum to the minimum temperature, which is close to 1.30. An analytical model of the diurnal variation is presented as a function of solar time and latitude. This model is used to eliminate the day-and-night effect in a study of the semi-annual temperature oscillation, whose amplitude is found to be related to solar activity in the same manner as the atmospheric temperature itself. The original explanation based on the solar wind now appears unlikely. A practical method for the computation of exospheric temperatures as a function of geographic, solar, and geomagnetic parameters is schematically presented. Author