High latitude minor ion enhancements: A clue for studies of magnetosphere-atmosphere coupling

Abstract

Unexpectedly abrupt and pronounced distributions of the thermal molecular ions NO +, O 2 + and N 2 + are observed at mid and high latitudes by the OGO-6 ion mass spectrometer. Normally considered trace constituents of the topside ionosphere, following magnetic storms these minor ions may reach concentration levels exceeding 10 3 ions/cm 3 at altitudes as great as 1000 km, suggestive of scale heights well in excess of those inferred from low and mid-latitude measurements, under relatively undisturbed conditions. The high latitude ion enhancements are sometimes observed to be narrowly defined in time and space, with molecular ion concentrations changing by as much as an order of magnitude between successive orbits. Assuming that these localized ion enhancements are associated with energetic perturbation of the lower ionosphere, it would follow that energy coupled to the lower altitudes may at times also be narrowly distributed in time and space within a given hemisphere. This view seems consistent with the observation that local magnetic substorm activity is closely associated in time and space with the anomalous ion enhancements. These results suggest that the search for a link between solar-magnetic processes and perturbation of the lower atmosphere may well benefit from phenomenological investigations, in support of statistical methods attempted previously.