Lower E-region MF radar spaced antenna measurements over magnetic equator

Abstract

Medium frequency (MF) radar spaced antenna observations at heights close to the location of the equatorial electrojet over Tirunelveli (8.7°N, 77.8°E, geographic, 0.35°N magnetic dip) are used to examine the influence of the electrodynamical processes in the determination of neutral winds in the lower E-region. On many days, daytime wind and tidal characteristics change at heights above , when analysis is performed on day-to-day basis. Under these conditions, the spaced antenna measurements need not represent neutral winds at all. On the other hand, on a few other days, the ‘drifts’ at are opposite to those expected from the electrodynamical considerations leading us to believe that we might be measuring neutral winds around this time. Selected days during the year 1995 bring out this complex nature of the spaced antenna measurements carried out over the magnetic equator. Ground-based geomagnetic field data provide information on the electrodynamical state of the equatorial ionospheric E-region.