Atomic nitrogen densities near the polar cusp

The neutral atmospheric composition spectrometer on board the Dynamics Explorer 2 spacecraft sampled several major and minor thermospheric gases including atomic nitrogen. We present here a selection of passes over the polar cusp that provide a quantitative measure of N densities in this region and provide evidence of localized density increases due to soft particle precipitation. Increases in N densities are frequently observed but are smaller than accompanying increases in N 2 densities. Our observations support earlier studies suggesting that (1) N densities increase more rapidly than O densities during periods of high solar EUV flux and (2) N densities are larger in the summer hemisphere than in the winter hemisphere. A series of passes in February 1983, late in the lifetime of DE 2, indicated N densities at 200 km altitude were a factor of 2 larger near the southern cusp than near the northern cusp.