Upper Atmosphere Heating near the Auroral Zones

Abstract

IT has long been supposed^1–5 that there is a significant heat input into the upper atmosphere at high latitudes—either by Joule heating^2,3 or by absorption of charged particles⁵. The density of the upper atmosphere certainly increases at times of geomagnetic disturbance^6,7 and the effects seem to be enhanced^8,9 at higher latitudes with a shorter time delay between the peak geomagnetic disturbance and the maximum density⁹. Recently DeVries¹⁰ has analysed air densities measured by the LOGACS accelerometer during the period of intense geomagnetic activity (a_P∼400) on May 25–26, 1967. The increase in density on the nightside auroral zone (crossed at ∼2230 h LT at a height of 190 km) coincided with the onset of activity and the increase propagated to mid-latitudes after a delay of a few hours.