TEC response at two equatorial stations in the African sector to geomagnetic storms

Olawepo, A.O.; Oladipo, O.A.; Adeniyi, J.O.; Doherty, Patricia H.

doi:10.1016/j.asr.2015.03.029

Cited by 6 publications

(4 citation statements)

References 25 publications

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“…4.50 ° E, dip -7.9 ° ), an equatorial station in West Africa. The GPS receiver at Ilorin is part of a network of Scintillation Network Decision Aid (SCINDA); which is a network of ground based receivers that monitors scintillations at the UHF and L band frequencies caused by electron density irregularities in the equatorial ionosphere (Olawepo et al., 2015). The DPS at Ilorin was installed in March 2010 and it acquired data continuously up till January 2011.…”

Section: Methodsmentioning

confidence: 99%

Storm time IRI-Plas model forecast for an African equatorial station

Adebiyi

Ikubanni

Adebesin

et al. 2019

Heliyon

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The limitation of ionospheric models in describing short-term ionospheric events has led to the development of data assimilative models e.g. the International Reference Ionosphere extended to Plasmasphere (IRI-Plas) model . This paper compares the IRI-Plas derived total electron content (TEC), the peak height (hmF2) and critical frequency (foF2) of the F2-layer with those obtained from Global Positioning System (GPS) receiver's and Digisonde Precision Sounder (DPS-4) measurements over Ilorin (Geog. Lat. 8.50 o N; Long. 4.50 o E, dip: – 7.9 o ) during geomagnetic storm days. The model estimation was done by assimilation of Ionosonde foF2 and TEC derived from GPS (GPS-TEC) and Global Ionospheric Map (GIM-TEC) into the model code. In order to study the effect of data assimilation on the model's representation, the “no input” option of the model was used as reference. The result shows that with the exception of the foF2 assimilation mode, all the options generally reproduced TEC quite well for all the storm days considered. Overall, the model adjusted with GPS-TEC gives the best prediction of TEC as it reduced the prediction error of TEC by a multiple of up to three compared to using the GIM-TEC. Also, all the options failed to reproduce the storm induced prominent features in the storm-time features of foF2 and hmF2. In other word, assimilation with the TEC does not generally improve the storm-time predictions of foF2 and hmF2 at the station. Consequently, for storm-time estimation of the F2-layer peak parameters, the ‘no input’ representation of the model is more valid at this station.

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Section: Methodsmentioning

confidence: 99%

Storm time IRI-Plas model forecast for an African equatorial station

Adebiyi

Ikubanni

Adebesin

et al. 2019

Heliyon

Self Cite

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“…facilitate to study the ionospheric response to geomagnetic storms with more insight [ de Abreu et al ., , , ; de Jesus et al ., , ; Sahai et al ., ; Zhang et al ., ] along with the fully coupled global ionosphere‐thermosphere models [ Crowley et al ., ; Fuller‐Rowell et al ., ; Lu et al ., ; Klimenko et al ., ; Sahai et al ., ]. The use of total electron content (TEC) measurements from dual frequency GPS receivers around the globe becomes a very powerful technique for ionospheric studies [ Fagundes et al ., ; Olawepo et al ., ].…”

Section: Introductionmentioning

confidence: 99%

“…The availability of extensive ground-based multisite observations and multiinstruments (all-sky imagers, Fabry-Perot interferometer, ionosonde, radar, TEC-GPS, etc.) facilitate to study the ionospheric response to geomagnetic storms with more insight [de Abreu et al, 2010[de Abreu et al, , 2014de Jesus et al, 2012de Jesus et al, , 2013Sahai et al, 2012;Zhang et al, 2015] along with the fully coupled global ionosphere-thermosphere models [Crowley et al, 2006 use of total electron content (TEC) measurements from dual frequency GPS receivers around the globe becomes a very powerful technique for ionospheric studies [Fagundes et al, 2015;Olawepo et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

Positive and negative GPS‐TEC ionospheric storm effects during the extreme space weather event of March 2015 over the Brazilian sector

et al. 2016

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We studied the response of the ionosphere (F region) in the Brazilian sector during extreme space weather event of 17 March 2015 using a large network of 102 GPS‐ total electron content (TEC) stations. It is observed that the vertical total electron content (VTEC) was severely disturbed during the storm main and recovery phases. A wavelike oscillation with three peaks was observed in the TEC diurnal variation from equator to low latitudes during the storm main phase on 17–18 March 2015. The latitudinal extent of the wavelike oscillation peaks decreased from the beginning of the main phase toward the recovery phase. The first peak extended from beyond 0°S to 30°S, the second occurred from 6°S to 25°S, whereas the third diurnal peaks was confined from 13°S to 25°S. In addition, a strong negative phase in VTEC variations was observed during the recovery phase on 18–19 March 2015. This ionospheric negative phase was stronger at low latitudes than in the equatorial region. Also, two latitudinal chains of GPS‐TEC stations from equatorial region to low latitudes in the east and west Brazilian sectors are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA) in the east and west Brazilian sectors. We observed an anomalous behavior in EIA caused by the wavelike oscillations during the storm main phase on 17 March, and suppression of the EIA, resulting from the negative phase in VTEC, in the storm recovery phase.

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“…TEC exhibits diurnal, seasonal, solar cycle, and geographical variations. Therefore, the physical and dynamical morphology of the TEC over a given location is of great importance in transionospheric communications during both quiet and disturbed geomagnetic conditions (Aravindan and Iyer, 1990;Akala et al, 2012;Olawepo et al, 2015;Tariku, 2015 andde Jesus et al, 2016). GPS TEC is quantified from the GPS orbiting satellites to the GPS receiver station on the Earth, with an approximate distance of 20 200 km (Liu et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Morphology of GPS and DPS TEC over an equatorial station: validation of IRI and NeQuick 2 models

et al. 2018

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Abstract. We investigated total electron content (TEC) at Ilorin (8.50∘ N 4.65∘ E, dip lat. 2.95) for the year 2010, a year of low solar activity in 2010 with Rz=15.8. The investigation involved the use of TEC derived from GPS, estimated TEC from digisonde portable sounder data (DPS), and the International Reference Ionosphere (IRI) and NeQuick 2 (NeQ) models. During the sunrise period, we found that the rate of increase in DPS TEC, IRI TEC, and NeQ TEC was higher compared with GPS TEC. One reason for this can be attributed to an overestimation of plasmaspheric electron content (PEC) contribution in modeled TEC and DPS TEC. A correction factor around the sunrise, where our finding showed a significant percentage deviation between the modeled TEC and GPS TEC, will correct the differences. Our finding revealed that during the daytime when PEC contribution is known to be absent or insignificant, GPS TEC and DPS TEC in April, September, and December predict TEC very well. The lowest discrepancies were observed in May, June, and July (June solstice) between the observed values and all the model values at all hours. There is an overestimation in DPS TEC that could be due to extrapolation error while integrating from the peak electron density of F2 (NmF2) to around ∼1000 km in the Ne profile. The underestimation observed in NeQ TEC must have come from the inadequate representation of contribution from PEC on the topside of the NeQ model profile, whereas the exaggeration of PEC contribution in IRI TEC amounts to overestimation in GPS TEC. The excess bite-out observed in DPS TEC and modeled TEC indicates over-prediction of the fountain effect in these models. Therefore, the daytime bite-out observed in these models requires a modifier that could moderate the perceived fountain effect morphology in the models accordingly. The daytime DPS TEC performs better than the daytime IRI TEC and NeQ TEC in all the months. However, the dusk period requires attention due to the highest percentage deviation recorded, especially for the models, in March, November, and December. Seasonally, we found that all the TECs maximize and minimize during the March equinox and June solstice, respectively. Therefore, GPS TEC and modeled TEC reveal the semiannual variations in TEC.

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TEC response at two equatorial stations in the African sector to geomagnetic storms

Cited by 6 publications

References 25 publications

Storm time IRI-Plas model forecast for an African equatorial station

Storm time IRI-Plas model forecast for an African equatorial station

Positive and negative GPS‐TEC ionospheric storm effects during the extreme space weather event of March 2015 over the Brazilian sector

Morphology of GPS and DPS TEC over an equatorial station: validation of IRI and NeQuick 2 models

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