THE STUDY OF LONGITUDINAL AND LATITUDINAL VARIATION OF EQUATORIAL ELECTROJET SIGNATURE AT STATIONS WITHIN THE 96°MM AND 210°MM AFRICAN AND ASIAN SECTORS RESPECTIVELY UNDER QUIET CONDITIONS.

Aniefiok Akpaneno,K R Ekundayo,Matthew Joshua

doi:10.33003/fjs-2021-0502-662

Abstract

Solar quiet current (S_q) and Equatorial Electrojet (EEJ) are two current systems which are produced by electric current in the ionosphere. The enhancement of the horizontal magnetic field is the EEJ. This research is needed for monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. This study presents the longitudinal and latitudinal variation of equatorial electrojet signature at stations within the 96°mm and 210°mm African and Asian sectors respectively during quiet condition. Data from eleven observatories were used for this study. The objectives was to determine the longitudinal and latitudinal geomagnetic field variations during solar quiet conditions, Investigate monthly variation and diurnal transient seasonal variation; Measure the strength of the EEJ at stations within the same longitudinal sectors and find out the factors responsible for the longitudinal and latitudinal variation of EEJ. Horizontal (H) component of geomagnetic field for the year 2008 from Magnetic Data Acquisition System (MAGDAS) network were used for the study. The International Quiet Days (IQDs) were used to identify quiet days. Daily baseline values for each of the geomagnetic element H were obtained. The monthly average of the diurnal variation was found. The seasonal variation of dH was found. Results showed that: The longitudinal and latitudinal variation in the dH differs in magnitude from one station to another within the same longitude due to the difference in the influence of the EEJ on them.

Highlights

One of the interesting geophysical phenomena associated with the equatorial ionosphere is the enhancement of geomagnetic variations on the ground at the equatorial stations when compared to those at off-equatorial latitudes
The general explanation of this effect is that the two dimensional current system in the sun lit part of the E-region of the ionosphere has a narrow band of enhanced current density almost parallel to the dip equator approximately in the west-east result in a counter electrojet (Forbes and Lindzen, 1976b; Takeda and Maeda, 1981; Hanuise et al, 1983)
The longitudinal geomagnetic field variation during solar quiet condition in dH is shown in Figures 2, 3 and 4 for diurnal basis across all stations with available data

Summary

Introduction

One of the interesting geophysical phenomena associated with the equatorial ionosphere is the enhancement of geomagnetic variations on the ground at the equatorial stations when compared to those at off-equatorial latitudes. The worldwide solar-driven variations at other latitudes, indicating that a CEJ is a result of a wind results in the Sq(solar quiet) current system in the E region of the Earth's ionosphere (100– 130 km altitude) Resulting from this current is an electrostatic field directed E-W (dawndusk) in the equatorial day side of the ionosphere. Global ionospheric current systems during the occurrence of CEJ events were examined by several authors (e.g., Takeda and Maeda, 1980b; Rastogi, 1994; Gurubaran, 2002; Yamazaki et al, 2012a) Those studies revealed the presence of additional current systems that are superposed on the normal Sq current within ± 3 degrees of the magnetic equator, known as the system. A counter equatorial electrojet (Roy, 1998)

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Conclusion