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

Wan Nur Izzaty Ismail,Nurul Shazana Abdul Hamid,Zahira Mohd Radzi,Akimasa Yoshikawa,Mardina Abdullah,Teiji Uozumi

doi:10.3390/universe7020023

Wan Nur Izzaty Ismail, Nurul Shazana Abdul Hamid + Show 4 more

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https://doi.org/10.3390/universe7020023

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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.

Highlights

The equatorial electrojet (EEJ) is the dayside current that circulates along the geomagnetic latitude within ±3◦ at the altitude of about 90 to 150 km within the E region of the ionosphere [1,2,3]
The longitudinal and local time variations of EEJ currents measured from ground and satellite data were analyzed in this study
The results were separated by local time (LT) and solar activity level

Summary

Introduction

The equatorial electrojet (EEJ) is the dayside current that circulates along the geomagnetic latitude within ±3◦ at the altitude of about 90 to 150 km within the E region of the ionosphere [1,2,3]. The global longitudinal profile of this current has been one of the most studied research subjects [7,8,9,10]. Studies on the longitudinal profile of the EEJ have been limited to a small number of observatories and satellite missions near the equator [6,11]. This is because our dip equator region lies over the oceans, thereby constraining the global analysis of the EEJ current.

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