Title: Latitudinal variations in the neutral atmospheric density
Abstract: In-situ atmospheric density measurements from the Explorer 32 density gages for the time period May through October 1966 reveal latitudinal density structure in the neutral thermosphere during geomagnetically undisturbed times. For altitudes between 300 and 700 km the summer northern latitude densities are greater than the equatorial densities. For latitudes greater than 55°N, the northern latitude to equatorial latitude density ratio is smallest during the day (near 1.3) and increases at night to values greater than 2. Large (>3) high-latitude to equatorial density ratios are observed near or in the auroral zone. These large ratios are observed even on geomagnetically quiet days. These results suggest that auroral zone and high latitude heating is a permanent feature of the summer thermosphere.