The electrodynamics of the low-latitude ionosphere: recent results and future challenges

Over the last few years, experimental and numerical modeling studies have provided extensive new information on the electrodynamics of the low-latitude ionosphere. Ground-based studies have determined the average seasonal, solar cycle and magnetic effects on the equatorial and low-latitude plasma drifts and thermospheric neutral winds, and their control over the F-region plasma density distribution. Satellite observations have been used, for the first time, to determine the latitudinal and longitudinal dependence of the F-region plasma drifts, and coordinated ground-based measurements have examined the global response of the low-latitude ionosphere to different high latitude forcing conditions. Recent studies have examined the coupling between storm-time thermospheric neutral winds and plasma drifts, and have determined the low-latitude signatures of magnetospheric and ionospheric dynamo electric fields. In this review, we initially examine the present understanding of low-latitude F-region electrodynamics focusing on the large-scale distribution of the ionospheric electric fields and their response to magnetospheric disturbances. We also discuss future initiatives necessary for a more complete understanding of these low-latitude transport processes. (C) 1997 Elsevier Science Ltd.