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

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.

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

“…In panel (b), the solid and dashed lines correspond to the results for the Southern Hemisphere and the Northern Hemisphere, respectively Forbush and Casaverde (1961), Hutton (1967); ∼ 62°W by Rastogi et al (2008); ∼ 45°W by Rigoti et al (1999), Rastogi et al (2010); for the African region ∼ 5°E by Onwumechili (1959), Ogbuehi and Onwumechilli (1963); ∼ 11 • E by Doumouya et al (1998); ∼ 16°E by Mayaud (1976a, 1976b); ∼ 39°E by Rastogi and Chandra (2015); for the Central Asian region ∼ 77°E by , Rabiu et al (2013); ∼ 81°E by Rastogi et al (2004); for the East Asian region ∼ 125°E by Yamazaki et al (2010). Comparisons of the equatorial electrojet intensities at various longitude sectors have revealed a strong dependence on the main field B (Rastogi 1962;Doumouya et al 2003;Abdul Hamid et al 2015). Figure 56a (from Doumouya et al 2003) illustrates the longitudinal dependence of the noon-time equatorial electrojet during the International Equatorial Electrojet Year (IEEY) (Abdu 1992), September 1991-March 1993.…”

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

“…Comparisons of the equatorial electrojet intensities at various longitude sectors have revealed a strong dependence on the main field B (Rastogi 1962;Doumouya et al 2003;Abdul Hamid et al 2015). Figure 56a (from Doumouya et al 2003) illustrates the longitudinal dependence of the noon-time equatorial electrojet during the International Equatorial Electrojet Year (IEEY) (Abdu 1992), September 1991-March 1993.…”

Response of Ionospheric Profile Parameters to Equatorial Electrojet Over Peruvian Station

“…This method of estimating EEJ is usually referred to as the two-station method. Other methods include the EE-index technique introduced by Uozumi et al (2008), the normalization technique proposed by Hamid et al (2014), where the geomagnetic observation data are normalized to the dip equator using the CM4 global current model (Sabaka et al, 2004), and the EEJ empirical model (Doumouya et al, 2003;Hamid et al, 2015). There remains a need for comparing these methods of estimating EEJ for an accurate representation of EEJ intensity, the subject of a future paper.…”