Observations of equatorial ionization anomaly over Africa and Middle East during a year of deep minimum

Abstract

Abstract. In this work, we investigated the veracity of an ion continuity equation in controlling equatorial ionization anomaly (EIA) morphology using total electron content (TEC) of 22 GPS receivers and three ground-based magnetometers (Magnetic Data Acquisition System, MAGDAS) over Africa and the Middle East (Africa-Middle East) during the quietest periods. Apart from further confirmation of the roles of equatorial electrojet (EEJ) and integrated equatorial electrojet (IEEJ) in determining hemispheric extent of EIA crest over higher latitudes, we found some additional roles played by thermospheric meridional neutral wind. Interestingly, the simultaneous observations of EIA crests in both hemispheres of Africa-Middle East showed different morphology compared to that reported over Asia. We also observed interesting latitudinal twin EIA crests domiciled at the low latitudes of the Northern Hemisphere. Our results further showed that weak EEJ strength associated with counter electrojet (CEJ) during sunrise hours could also trigger twin EIA crests over higher latitudes.

Statistical analysis of the correlation between the equatorial electrojet and the occurrence of the equatorial ionisation anomaly over the East African sector

“…Therefore, in our calculation of EIA strengths, the VTEC over ARMI was considered as that of the trough, while the VTEC over other stations with latitudes ranging 8-19.5 • S were considered as VTEC data at the crest. Our results during the high solar activity period of 2011-2013 differ in some aspects from the study done during the low solar activity year of 2009 reported by Bolaji et al (2017). For instance, their study revealed that the daytime EIA occurrence rarely exceeds 18:00 LT and there was practically no occurrence of the EIA past this time.…”

“…These three examples clearly show that high EEJ strengths occur simultaneously with the prominent EIA. This observation is similar to the one made by Bolaji et al (2017). Their results showed experimental evidence of how EEJ strength, which is a proxy of E × B drift, mostly controls plasma transportation over low latitudes.…”

“…2a, b, d and e is the occurrence of a second southern EIA crest spanning the magnetic latitude ∼ 28-40 • S. Figures 4 and 5 of Bolaji et al (2017) also depict these features over the southern low-and mid-latitude regions of East Africa. However, their emphasis was on the same feature that was observed north of the magnetic equator.…”

“…Yizengaw et al, 2010;Olwendo et al, 2015) and quiet conditions (Bolaji et al, 2017). The study by Bolaji et al (2017) used data during quiet geomagnetic and low solar activity conditions in the year 2009 to confirm the roles of the EEJ and integrated EEJ (IEEJ) in determining the hemispheric extent of the EIA crest over African mid-latitudes and low latitudes. They reported that, in the Southern Hemisphere, EIA crests can be seen in the magnetic latitudes ranging from about 17 to 19 • S.…”

Quantitative Characteristics of Equatorial Ionization Gradient Above 150 km at Low Solar Activity

“…They reported a steady diurnal monthly variation between the pattern of TEC and f o F 2 from predawn minimum to afternoon maximum and then decreases after sunset. Bolaji et al () investigated the veracity of the ion continuity equation in the control of equatorial ionization anomaly (EIA) morphology using TEC and the Magnetic Data Acquisition System across some Africa‐Middle East stations. They reported an extremely different morphology in the simultaneous observations of the EIA crests in both hemispheres of the Africa‐Middle East sector in comparison with the report obtained from the Asian sector.…”