Latitude and diurnal variations of air densities from 190 to 280 km as derived from the orbits of Discoverer satellites

Variations in air density between day and night in the region 190 to 280 km are found to be small (less than about 25%). The presence of a ‘wiggle’ in the curve of log (day-time density) against height indicates a possible region of local heating at about 220 km which disappears at night. The night-time density profile conforms with a constant scale height of 35(± 2) km. No definite variation of air density with latitude is evident apart from a possible increase of about 60%, which is indicated by rather limited polar-region data. For other latitudes and seasons a variation of less than about 20% is indicated.