STORM-TIME VARIATIONS OF ELECTRON CONCENTRATION IN THE EQUATORIAL TOPSIDE IONOSPHERE By

Storm-time variations of the topside ionosphere in equatorial latitudes over the American zone are examined, by using Alouette I sounding data. Three typical types of variations of electron concentration during geomagnetic storms are recognized. First type is characterized by the development of the equatorial anomaly, and second one by the disappearance of the anomaly. The occurrence of electron concentration enhancement without the anomaly over wide range of latitudes is third type. 1