Spectral analyses of night atmospheric emission observations from the S3--4 satellite revealed enhanced OI 1304-¿, OI 1356-¿, and OI 1640-¿, NI 1493-¿, NI 1744-¿ and NII 2143-¿ lines and Lyman-Birge-Hopfield (LBH) band emissions at low magnetic latitudes. The satellite, at about 260-km altitude, was over the region between -41¿ to -15¿ geomagnetic latitudes at 7:55 UT on August 28, 1978 (Dst=-193) during the main phase of a major geomagnetic storm (Maximum Dst=-242 at 10 UT).

The observed ratios of the LBH bands to the NI 1493-¿ and NI 1744-¿ line emissions are an order of magnitude lower than those produced by electron impact and are similar to laboratory measurements of heavy particle impact (H and H+) on N2. Significant precipitation of neutral O atoms, formed by charge exchange of the ring current O+ with exospheric hydrogen and oxygen, can occur when ‖Dst‖ is large. Oxygen is observed to dominate the ring current at corresponding low L-values during a storm main phase. Consideration of these and other factors leads us to conclude that the most likely cause of the observed emissions is oxygen precipitation from the ring current. ¿ American Geophysical Union 1992