ION GAUGE MEASUREMENTS OF LATITUDINAL DENSITY VARIATIONS AT NIGHT

Atmospheric densities have been obtained from a cold cathode ion gauge flown on the satellite 1972-32A in April-May 1972. The satellite orbit was inclined at 81.5 degrees in a noon-midnight configuration. Data obtained at heights between ZOO and 275 km during a geomagnetically quiet period have been examined for latitudinal effects. Transformed to a constant altitude of 230 kin, the data show a variation on the dark side by as much as a factor of 2, the highest density being at high northern latitudes and the lowest at middle to high southern latitudes. General agreement was obtained between the data and both the Jacchia-1971 and OGO-6 models. An equatorial maximum was sometimes observed that closely resembled the pure N-2-distribution as described by the OGO-6 model.