Comparison of EEJ Longitudinal Variation from Satellite and Ground Measurements over Different Solar Activity Levels

Abstract

The longitudinal variability and local time of equatorial electrojet (EEJ) current using simultaneous data recorded by ground and satellite magnetometers at different levels of solar activity were investigated. In this study, we used data from the CHAMP and Swarm satellites to obtain EEJ current measurements around the globe. The ground data were provided by the MAGDAS, INTERMAGNET, and IIG networks. The ground observation was carried out by analyzing magnetometer data in four different sectors: the South American, Indian, African, and Southeast Asian sectors. These ground data were normalized to the dip equator to overcome the latitudinal variation of each station. The analysis for both measurements was performed using quiet day data. Both the ground and satellite data were categorized according to solar activity level; low, moderate, and high. The results revealed that, during the low solar activity, there was a good agreement between the longitudinal profiles of the EEJ measured using the satellite and the ground data. In general, strong correlations were obtained in most of the sectors where ground data were available between 11 and 13 local time (LT). Besides that, our analysis revealed that the different times of maximum EEJ appearances were seasonally dependent only at certain longitude sectors.