Latitudinal dependence of the diurnal density variation

Atmospheric density measurements from the density gages on the Explorer 32 satellite have been used to determine in part the latitudinal dependence of the diurnal density variation. The data cover the period May–October 1966. The midlatitude densities for summer in the northern hemisphere confirm the diurnal variation reported from analysis of satellite drag data. However, the data for high northern latitudes (61°) show that the diurnal density variation is less than expected, and that the nighttime densities are greater than expected (the day to night temperature ratio is 1.02). These effects cause a latitudinal gradient in the diurnally averaged densities with increasing density toward the pole. The diurnally averaged density values are consistent with a heat source at high latitude and have a tendency to be better ordered with geomagnetic latitude. This indicates that perhaps a persistent heat source for the neutral atmosphere is associated with the auroral zone.