Electron concentration variations in the topside ionosphere between 60°N and 60°S geomagnetic latitude associated with geomagnetic disturbances

Abstract

Variations of electron concentration in the topside ionosphere associated with geomagnetic disturbances were analyzed between 60°N and 60°S geomagnetic latitude over the American continents, using Alouette 1 satellite data. Twenty individual storm-time variation profiles of electron concentration were derived. In low and equatorial latitudes two types of profiles, D and N, were observed. The D-type profile, which is composed of both enhancement and reduction parts, occurs in the daytime in the majority of cases, whereas the N type, characterized by enhancement, seems to occur mainly at night. In the midlatitudes no definite daytime and nighttime profiles were found, though an enhancement was observed most often at 25° ∼ 35° geomagnetic latitudes, and a reduction was observed at 45° ∼ 55°. Relationships between latitudinal and height extents, magnitudes of the storm-time variation of the electron concentration, Kp index, and season were not clear in this analysis. A qualitative explanation was attempted for these results, based on electron drift due to electromagnetic forces and ambipolar diffusion. This explanation seems to be applicable at least at low and equatorial latitudes.