Variations in the low- and middle-latitude topside ion concentration observed by DMSP during superstorm events

Observations of the topside ion number density by the DMSP satellites on the dayside near 0930 LT and near dusk describe a characteristic evolution during the course of three superstorm events in November 2001, November 2003, and November 2004. Density enhancements at middle latitudes and at the equator may be identified as separate features that may appear together but can evolve independently. These characteristics are consistent with the action of both upward ( outward) E x B drifts and equatorward neutral winds and it is suggested that both F region drivers are required to reproduce the observed behavior on these occasions. Upward excursions of the E x B drift at the equator may be short- lived compared to the satellite orbit period of about 100 min but may also exist for longer periods under the influence of penetration fields and modified dynamo fields. Upward drifts at middle latitudes may be induced by meridional winds and by the high- latitude convection pattern as it expands to latitudes as low as 40 degrees magnetic.