Total electron content and magnetic field intensity over Ilorin, Nigeria

Bolaji, O. S.; Adeniyi, J.O.; Adimula, I. A.; Radicella, S. M.; Doherty, Patricia H.

doi:10.1016/j.jastp.2013.02.011

Cited by 19 publications

(33 citation statements)

References 60 publications

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“…This is one of the parameters of transportation in the ion continuity equation (Rishbeth, 1962;Lei et al, 2008). Significantly, it drifts plasma from the equatorial latitude along the magnetic field lines to higher latitudes under the influence of gravity and pressure gradients (Martyn, 1947;Bolaji et al, 2013). A good representation of the equatorial eastward electric field is EEJ strength (Anderson et al, 2002), and IEEJ strength up to a daily maximum (Venkatesh et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…From our results that showed a maximum magnitude of ∼ 49 nT around 12:00 LT associated with a significant CEJ (∼ 48 nT) around 09:00 LT, this EEJ strength variability (7 April) indicates a weaker eastward daytime electric field during sunrise hours and that a pre-noon EIA crest could not be formed. Investigations into pre-noon peaks of TEC and electron density at the F2-layer (NmF2) over the equatorial latitudes have been made by Skinner (1966), Rajaram (1977), Radicella and Adeniyi (1999), Lee and Reinisch (2006), and Bolaji et al (2012Bolaji et al ( , 2013. They reported that development of a prenoon EIA crest is due to a stronger eastward daytime electric field compared to photoionization near noon.…”

Section: Discussionmentioning

confidence: 99%

“…The EEJ strength is evaluated by subtracting the S q deduced from the H-field intensity (Bolaji et al, 2013) located outside the equatorial latitude at about ±5 to ±10 • latitudes from the one located within the equatorial latitude of ±3 • (Rastogi and Klobuchar, 1990;Anderson et al, 2002;Chen et al, 2008 The EEJ strength was estimated for both hemispheres, where the northern and southern EEJ strengths are represented with EEJ N and EEJ S respectively. In addition, the daytime integrated EEJ strength values for both the hemispheres were evaluated by integrating all the hourly EEJ strengths from 07:00 to 12:00 LT.…”

Section: Equatorial Electrojet (Eej) and Its Integrated (Ieej) Strengthmentioning

confidence: 99%

“…Chen et al (2008) and Venkatesh et al (2015) also investigated EIA morphology without considering selection of the quietest days for the estimates of solar quiet (S q ). Apart from the fact that the S q current system is crucial to the estimates of EEJ strength (Rastogi and Klobuchar, 1990;Anderson et al, 2002;Bolaji et al, 2015), the response of EIA to EEJ strength during the quietest period has not been carried out over the African-Middle Eastern sector. One critical question that needs answered in order to improve our understanding of EEJ and IEEJ strength roles in the formation of fountain effect over Africa-Middle East is whether the responses of EIA to EEJ strength variability investigated in other regions be used as representations of African-Middle Eastern morphology.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Equatorial Electrojet (Eej) and Its Integrated (Ieej) Strengthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…The VTEC data estimated are then subjected to a two-sigma (2σ ) iteration, which is a measure of GPS point positioning accuracy (95 % confidence level). Research efforts that have utilized this GPS TEC software include the works of Bolaji et al (2012Bolaji et al ( , 2013, Olwendo et al (2013), Rabiu et al (2014), and Ayorinde et al (2016), among others.…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

et al. 2017

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Abstract. The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes -4.33 and 0.72 • N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25-30 TECU) around equinoxes and lower values (∼ 20-25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes.

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Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

et al. 2015

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We have used chains of Magnetic Data Acquisition System (MAGDAS) magnetometer records of the horizontal (H) and vertical (Z) magnetic field intensities during September 2008 to August 2009 (year of deep minimum) across Africa to study their variability during the quietest international days, which coincidently associated with the sudden stratospheric warming (SSW) event in January 2009. This selection of the most international quiet days is indicative of 80% that are strongly associated with days when unusually strong and prolonged sudden SSW event occurs in January 2009. Interestingly, in January, a significant magnitude depletion of solar quiet (S q ) equivalent current was observed near noon hours around the magnetic equator (Addis Ababa, ABB) compared to any other months along with a consistent significantly reduced value across the Northern Hemisphere and moderate decrease at the Southern Hemisphere. Also, we found that Nairobi and Dar es Salaam at the Southern Hemisphere, which are close to ABB (dip equator), are strongly prone to westward electric field compared to the magnetic equator and Khartoum at the Northern Hemisphere. Significant negative values of MS q (Z) magnitudes observed near noon hours at Hermanus indicate the presence of induced currents that suggest ocean effects along with reversal to significant positive values in the afternoon, which subsided before 1800 LT in almost all the months, indicate stronger influence of ionospheric currents. On seasonal variability of S q (H), a slight depression at ABB during September equinox is one of the evidences of seasonal S q focus shift. Latitudinal variability of S q near-noon hours was also investigated.

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Total electron content and magnetic field intensity over Ilorin, Nigeria

Cited by 19 publications

References 60 publications

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

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

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

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