GUVI limb observations of the Equatorial Ionization Anomaly

High altitude limb scans from Global Ultra Violet Imager (GUVI) contain signatures of the Equatorial Ionization Anomaly (EIA) observed using 1356 Å recombination emissions. This paper reports observations of the geomagnetic quiet time EIA and its global behavior at all local times, longitudes and seasons. Limb data is prepared for analysis using reduction techniques that remove from the limb file, contaminating signatures due to stars, glints and low altitude day time neutral atmosphere glow due to photoelectrons. A simple comparison of the subtracted data at different longitudes, seasons and magnetic activity reveal significant EIA variability with each of these factors. This data set integrated in altitude, is used to develop the global morphology of the quiet time EIA using metrics such as the magnetic latitudes of the north and south crest and the crest radiances that are extracted from the EIA structures. Observations from year 2003 to 2005 clearly show development in the anomaly strength between 11:00 to 14:00 LT. Signatures of the pre-reversal drift enhancement due to enhanced post-sunset F-region vertical drifts appear strongly during December solstice seasons between 19:00 to 21:00 local time at solar maximum periods. However this effect is found to be unexpectedly absent during equinox. Also observed is the lack of any EIA activity during June solstice during all the three years.