Empirical model of equatorial electrojet based on ground-based magnetometer data during solar minimum in fall

Nurul Shazana Abdul Hamid,Akimasa Yoshikawa,Teiji Uozumi,Huixin Liu

doi:10.1186/s40623-015-0373-1

Nurul Shazana Abdul Hamid, Akimasa Yoshikawa + Show 2 more

Open Access

https://doi.org/10.1186/s40623-015-0373-1

Copy DOI

Abstract

In this study, we constructed an empirical model of the equatorial electrojet (EEJ), including local time and longitudinal dependence, based on simultaneous data from 12 magnetometer stations located in six longitude sectors. An analysis was carried out using the equatorial electrojet index, EUEL, calculated from the geomagnetic northward H component. The magnetic EEJ strength is calculated as the difference between the normalized EUEL index of the magnetic dip equator station and the normalized EUEL index of the off-dip equator station located beyond the EEJ band. Analysis showed that this current is always strongest in the South American sector, regardless of local time (LT), and weakest in the Indian sector during 0900 and 1000 LT, but shifted to the African sector during 1100 to 1400 LT. These longitude variations of EEJ roughly follow variations of the inversed main field strength along the dip equator, except for the Indian and Southeast Asian sectors. The result showed that the EEJ component derived from the model exhibits a similar pattern with measured EEJ from ground data during noontime, mainly before 1300 LT.

Highlights

The equatorial electrojet current has always been conceived as a phenomenon confined to a narrow area around ±3° of the dip equator
For each local time from 0900 to 1500, the longitudinal profile of EEJ showed that this current was strongest in the South American sector and weakest in the African sector, unlike the observation data where EEJ was the smallest in the Indian sector during 0900 and 1000 LT, but shifted to the East African sector
The EEJ longitudinal profile obtained is similar to the one shown by Doumouya and Cohen (2004), with some discrepancy appearing in the African sector, where our result shows a decreasing trend in this sector while their result shows a small increasing trend

Summary

Introduction

The equatorial electrojet current has always been conceived as a phenomenon confined to a narrow area around ±3° of the dip equator. Previous study by Hamid et al (2014) has successfully separated equatorial electrojet (EEJ) and Sq at the dip equator observed from three longitude sectors: South America, India, and Southeast Asia.

Results

Conclusion