Electric fields in the equatorial ionosphere derived from CHAMP satellite magnetic field measurements

system, equatorial vertical ion drifts, and the equatorial ionization anomaly (EIA). Due to its importance, there is much interest in accurately measuring the EEF. However, there is a severe lack of high quality data with the notable exception being the JULIA coherent scatter radar in Peru. In this work, we use CHAMP satellite-derived latitudinal current profiles of the day-time EEJ in order to estimate the eastward electric field at all longitudes, seasons, and day-side local times. We have constructed a dataset of over 32,000 EEF estimates based on six years of CHAMP data. Our estimates agree well with JULIA measurements, with an RMS difference of 0.13mV/m. & 2009 Elsevier Ltd. All rights reserved.