Monitoring the Daytime Variations of Equatorial Ionospheric Anomaly Using IONEX Data and CHAMP GPS Data

A method, which can invert the ionospheric electron content above the CHAMP satellite, is presented. The daytime behavior of the equatorial ionospheric anomaly (EIA) is monitored using the CHAMP global positioning system data and the ionosphere map exchange format data supplied by the Center for Orbit Determination in Europe during the period at quiet geomagnetic conditions between November 7 and December 12, 2003. Results show that the plasma congregates and rises above the geomagnetic equator due to the daytime upward vertical E x B drift during the early variations of EIA. After being lifted to higher altitudes, the topside ionospheric equatorial plasma above the CHAMP orbit (over 400 km above the ground) controlled mainly by the electromagnetic field starts to diffuse downward to higher latitudes along magnetic field lines, and the double-humped structure begins to appear in the topside ionosphere above the CHAMP orbit. However, a single crest is still observed for the entire ionosphere above the ground, and this single peak moves slightly to the winter hemisphere as a result of the transequatorial neutral wind. With the continuous diffusion of the plasma, the two crests also occur for the entire ionosphere at both sides of the geomagnetic equator.