Major phenomena of the equatorial ionosphere-thermosphere system under disturbed conditions

We present here a brief review of recent results related to the response of the major phenomena of the equatorial ionosphere-thermosphere system (EITS) to magnetospheric disturbances. Modifications to the equatorial ionization anomaly (EIA), equatorial spread F (ESF) and equatorial electrojet (EEJ) are produced by (a) disturbance electric fields resulting from prompt equatorward penetration of magnetospheric/high latitude electric fields, (b) disturbance dynamo driven by enhanced global thermospheric circulation resulting from energy input at high latitude, and (c) disturbance winds (zonal and meridional) modifying the equatorial thermospheric dynamics. While the disturbance electric fields could cause enhanced development or inhibition of these phenomena the disturbance winds seem to always inhibit them, especially the EIA and ESF. New results discussed concern the role of meridional winds in the disturbance electric field induced F layer height response over low latitudes, evidence on ESF/plasma bubble inhibition by disturbance meridional/trans-equatorial wind, EIA expansion in latitude reaching spectacular magnitude during intense storms, longitudinal/local time dependence of EIA enhancements; and common sources of ESF and EIA response features and related aspects, among others. We advance, further, suggestions on specific studies to be pursued for better understanding of the problems presented. (C) 1997 Elsevier Science Ltd.