Relationship between the equatorial electrojet and global Sq currents at the dip equator region

Abstract

The equatorial electrojet (EEJ) is a strong eastward ionospheric current flowing in a narrow band along the dip equator. In this study, we examined the EEJ-Sq relationship by using observations at six stations in the South American, Indian, and Southeast Asian sectors. The analysis was carried out with data on geomagnetically quiet days with Kp ≤3 from 2005 to 2011. A normalization approach was used because it yields more accurate results by overcoming the uncertainties due to latitudinal variation of the EEJ and Sq. A weak positive correlation between the EEJ and Sq was obtained in the Southeast Asian sector, while weak negative correlations were obtained in the South American and Indian sectors. EEJ-Sq relationship is found to be independent of the hemispheric configuration of stations used to calculate their magnetic perturbations, and it also only changed slightly during low and moderate solar activity levels. These results demonstrate that the Southeast Asian sector is indeed different from the Indian and South American sectors, which is indicative of unique physical processes particularly related to the electro-dynamo. Furthermore, we also demonstrate that the definition of the EEJ, that is, the total current or enhanced current, can significantly affect the conclusions drawn from EEJ-Sq correlations.

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…In many cases, poor correlation was found (Osborne 1963(Osborne , 1966(Osborne , 1968Ogbuehi et al 1967;Schlapp 1968;Mann and Schlapp 1988;Manoj et al 2006;Abdul Hamid et al 2014). The results were often taken as evidence that the equatorial electrojet is not a simple enhancement of Sq currents and hence other driving mechanisms exist for the EEJ.…”

Nighttime Pc3 pulsations: MM100 and MAGDAS observations

“…The bibliography on a possible relation of wave geomagnetic phenomena with global current systems, such as auroral and equatorial electrojets, storm-time current systems, and solar quiet system, includes several hundred publications (see e.g., Stening 1995;Hamid et al 1967). However, this problem is far from being solved.…”

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

“…This approach, introduced by Hamid et al (2014), helps to minimize uncertainties due to the latitudinal variation of both EEJ and Sq currents. The normalized Sq at the dip equator [EUEL (0°)] is obtained from the normalization of EUEL data of stations at the off-dip equator [EUEL (θ°)], using the following formula:…”

“…Both currents overlap at the dip equator to give the total current and significantly affect the geomagnetic data measured in the area (Forbes 1981;Stening 1995;Onwumechili 1997). 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. The normalization approach suggested by them gives an opportunity to construct an EEJ empirical model based on observational data, mainly from ground-based magnetometers, regardless of the effect of EEJ and Sq latitudinal variations.…”