Simultaneity and Asymmetry in the Occurrence of Counterequatorial Electrojet along African Longitudes

Rabiu, A. B.; Folarin, Olanike Olufunmilayo; Уозуми, Т.; Yoshikawa, Akimasa

doi:10.1002/9781118929216.ch2

Cited by 4 publications

(7 citation statements)

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“…In order to compute the EEJ current, the solar quiet daily variation ( Sq ) horizontal magnetic intensity values for the pairs of stations in both longitudinal sectors were estimated following the procedure outlined by Rabiu et al. (2017). The daily EEJ current was obtained by subtracting the daily horizontal magnetic field intensity ( Sq ) data of a station located outside the equatorial region, that is, Adigrat (magnetic latitude: 6.00°N) from those of the station within the equatorial region, that is, Addis Ababa (0.17°N) in the African longitudinal sector.…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

“…In addition, this study used EEJ current to infer the vertical E × B drift during the SSW events (Anderson et al., 2002, 2004; Bolaji et al., 2019; Rabiu et al., 2017; Yizengaw et al., 2014). This sampled one‐minute horizontal magnetic field intensity data obtained from the African Meridian B‐Field Education and Research, AMBER (http://magnetometers.bc.edu/), International Real‐time Magnetic Observatory Network, INTERMAGNET (http://www.intermagnet.org) and the Low Ionospheric Sensor Network, LISN (http://lisn.igp.gob.pe/jdata) were used to determine EEJ ( nT ).…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

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African and American Equatorial Ionization Anomaly (EIA) Responses to 2013 SSW Event

2022

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This study investigates the responses of the African and American Equatorial Ionization Anomaly (EIA) regions to 2013 Sudden Stratospheric Warming (SSW) event. The Total Electron Content (TEC) data obtained from chains of Global Positioning System receivers within ±40° geomagnetic latitudes in the African and American sectors were used to construct the EIA structures for both longitudinal sectors. The responses of the EIA structures, constructed from the TEC, ΔTEC, and ionospheric irregularities data to the 2013 SSW event were investigated. During the SSW peak phase, EIA structures in both longitudinal sectors responded significantly, with the pole‐ward flow of plasma from the equator to higher crests' locations (strengthening of the EIA). Furthermore, a clear asymmetry in plasma distribution in the northern and southern crests of the EIA was observed. Generally, for the entire data span, TEC enhancements and ionospheric irregularities occurrences during SSW were more in the American sector than the African sector. The geomagnetic activity of 17 January 2013 caused negative TEC response in the African sector and positive TEC response in the American sector. Moderate storm‐induced TEC enhancements were generally lower than SSW‐induced TEC enhancements. Furthermore, solar flux‐induced TEC of 10 January 2013 was lesser than the SSW‐induced TEC of 15–16 January 2013.

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Section: Data and Methods Of Analysismentioning

confidence: 99%

Section: Data and Methods Of Analysismentioning

confidence: 99%

African and American Equatorial Ionization Anomaly (EIA) Responses to 2013 SSW Event

2022

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“…The EEJ current was processed using the procedure outlined by Rabiu et al. (2017). The EEJ current was calculated using the expression below:

EEJ = Δ H_{eq} - Δ H_{off ‐ eq}

where Δ H eq is the horizontal magnetic field intensity for a station located at equatorial region and Δ H off‐eq is the horizontal magnetic field intensity for a station located outside the equatorial regions.…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

“…In the American sector, both the equatorial and low-latitude magnetometers data at Jicamarca (0.8°N, 5.7°W) and Plura (6.8°N, 9.4°W) were obtained from the Low Ionospheric Sensor Network (LISN) (http://lisn.igp.gob.pe/data/). The EEJ current was processed using the procedure outlined by Rabiu et al (2017). The EEJ current was calculated using the expression below:…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

Responses of the African and American Equatorial Ionization Anomaly (EIA) to 2014 Arctic SSW Events

2021

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“…The EEJ strength was calculated using the procedure of [53], where the data used are from the same stations in the American, African, and Asian sectors. The geomagnetic stations are listed in Table 2, and the EEJ strength is estimated by the following equation [54]: In this equation, ∆H eq and ∆H off_eq are the differential horizontal magnetic field intensity (transient variation) for the stations at the equatorial dip region and outside the equatorial region, respectively.…”

Section: Penetration Electric Fields Equatorial Electrojet and Curren...mentioning

confidence: 99%

Low-Latitude Ionospheric Responses and Coupling to the February 2014 Multiphase Geomagnetic Storm from GNSS, Magnetometers, and Space Weather Data

et al. 2022

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The ionospheric response and the associated mechanisms to geomagnetic storms are very complex, particularly during the February 2014 multiphase geomagnetic storm. In this paper, the low-latitude ionosphere responses and their coupling mechanisms, during the February 2014 multiphase geomagnetic storm, are investigated from ground-based magnetometers and global navigation satellite system (GNSS), and space weather data. The residual disturbances between the total electron content (TEC) of the International GNSS Service (IGS) global ionospheric maps (GIMs) and empirical models are used to investigate the storm-time ionospheric responses. Three clear sudden storm commencements (SSCs) on 15, 20, and 23 February are detected, and one high speed solar wind (HSSW) event on 19 February is found with the absence of classical SSC features due to a prevalent magnetospheric convection. The IRI-2012 shows insufficient performance, with no distinction between the events and overestimating approximately 20 TEC units (TECU) with respect to the actual quiet-time TEC. Furthermore, the median average of the IGS GIMs TEC during February 2014 shows enhanced values in the southern hemisphere, whereas the IRI-2012 lacks this asymmetry. Three low-latitude profiles extracted from the IGS GIM data revealed up to 20 TECU enhancements in the differential TEC. From these profiles, longer-lasting TEC enhancements are observed at the dip equator profiles than in the profiles of the equatorial ionospheric anomaly (EIA) crests. Moreover, a gradual increase in the global electron content (GEC) shows approximately 1 GEC unit of differential intensification starting from the HSSW event, while the IGS GIM profiles lack this increasing gradient, probably located at higher latitudes. The prompt penetration electric field (PPEF) and equatorial electrojet (EEJ) indices estimated from magnetometer data show strong variability after all four events, except the EEJ’s Asian sector. The low-latitude ionosphere coupling is mainly driven by the variable PPEF, DDEF (disturbance dynamo electric fields), and Joule heating. The auroral electrojet causing eastward PPEF may control the EIA expansion in the Asian sector through the dynamo mechanism, which is also reflected in the solar-quiet current intensity variability.

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Simultaneity and Asymmetry in the Occurrence of Counterequatorial Electrojet along African Longitudes

Cited by 4 publications

References 50 publications

African and American Equatorial Ionization Anomaly (EIA) Responses to 2013 SSW Event

African and American Equatorial Ionization Anomaly (EIA) Responses to 2013 SSW Event

Responses of the African and American Equatorial Ionization Anomaly (EIA) to 2014 Arctic SSW Events

Low-Latitude Ionospheric Responses and Coupling to the February 2014 Multiphase Geomagnetic Storm from GNSS, Magnetometers, and Space Weather Data

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