Bibliography

The African equatorial ionization anomaly response to the St. Patrick’s Day storms of March 2013 and 2015

The ionosphere around the Equatorial Ionization Anomaly (EIA) region exhibits complex dynamics and responds markedly to the solar-magnetospheric energy and momentum. In this paper, the hourly total electron content (TEC) variations in response to the EIA structure in Africa to the 2013 and 2015 St. Patrick’s Day storms is investigated using data obtained from a chain of GPS receivers located in the Africa region. The TEC variations are characterized based on the convective magnetospheric dynamo fields, neutral wind circulation, and zonal electric fields. Generally, the result indicates that the TEC variations are consistent with the different directions of the interplanetary fields during the different phases of the storms. We observed reverse EIA structures in the main phase of the March 2015 storm, likely to be related to the intense PPEF and strong equatorward wind, which imposed a westward zonal electric field at the equator. A similar equatorial peak observed during the recovery phase is associated with DDEF, poleward wind and plasma convergence. Furthermore, the TEC variations also indicate hemispheric asymmetries during the storms. During the main phase of the storm, the TEC variation is more enhanced in the Northern Hemisphere in March 2013 and reverses during March 2015. We observed an equatorial peak during the SSC period in March 2013, while EIA structures are generally weak in March 2015 event. This posit that ionospheric pre-storm behaviour in the EIA region can be better understood when the IMF-Bz and E-field are not significant. The observed distinctive response avowed the peculiarity of the electrodynamics intricacy in the Africa sector.

Bolaji, Olawale; Adekoya, Bolarinwa; Adebiyi, Shola; Adebesin, Babatunde; Ikubanni, Stephen;

Published by: Astrophysics and Space Science      Published on: jan

YEAR: 2022     DOI: 10.1007/s10509-021-04022-5

TEC; EIA; DDEF; Plasma reversal; PPEF; Pre-storm

Latitudinal Dependence of Ionospheric Responses to Some Geomagnetic Storms during Low Solar Activity

The Latitudinal dependence in the response of the Ionospheric F2-layer electron density (NmF2) and peak height (hmF2) to three geomagnetic storms of May and August 2010 has been examined. The data-sets used for the study were obtained from Ilorin, Nigeria (1.87° S/76.67° E), San Vito, Italy (34.68° N/90.38° E), Hermanus, South Africa (42.34° S/82.15° E), and Pruhonice, Czech Republic (45.66° N/90.38° E) geomagnetic coordinates. The quiet time result shows that the rise in NmF2 began earlier at San Vito, followed by Pruhonice. The rate of ionization was observed to be highest in Ilorin, while, the rate of decay in NmF2 is faster at Hermanus. For disturbed NmF2 condition, remarkable similarities in the NmF2 responses during geomagnetic storms were recorded from Hermanus in the mid-latitude and Ilorin, an equatorial station. NmF2 enhancements (\textgreater6 hours) that is consistent with the increase in hmF2 were observed at all the mid-latitude stations during the main phase of the 02 May, 2010 storm, without any noticeable change over ILN. Similarly, 12 hours of positive phase was observed at ILN and HMN, with 30 hours of NmF2 depletions at PRN and SVT during the recovery phase. ILN is in the equatorial Trough, so most of the NmF2 produced at this region is lifted to the higher latitudes by the fountain effect during the main phase. The suppression of the zonal electric field at ILN is responsible for the NmF2 enhancement during the recovery phase, while the mid-latitude responses have been attributed to the effect of the thermospheric winds and neutral composition changes.

Joshua, B.; Adeniyi, J.; Olawepo, A.; Rabiu, Babatunde; Daniel, Okoh; Adebiyi, S.; Adebesin, B.; Ikubanni, S.; Abdurahim, B.;

Published by: Geomagnetism and Aeronomy      Published on: may

YEAR: 2021     DOI: 10.1134/S0016793221030063

Electric field; Electron density; Geomagnetic storms; magnetosphere; peak height

Response of GPS-TEC in the African equatorial region to the two recent St. Patrick s day storms

The 2015 St. Patrick’s Day storm is one of the most intense geomagnetic storm in this present solar cycle (SYM-H=-213nT). In this paper, we investigate the response of the African low

Ikubanni, SO; Adebiyi, SJ; Adebesin, BO; Dopamu, KO; Joshua, BW; Bolaji, OS; Adekoya, BJ;

Published by: International Journal of Civil Engineering and Technology      Published on:

YEAR: 2018     DOI:

GPS derived TEC and foF2 variability at an equatorial station and the performance of IRI-model

The ionosphere induces a time delay in transionospheric radio signals such as the Global Positioning System (GPS) signal. The Total Electron Content (TEC) is a key parameter in the mitigation of ionospheric effects on transionospheric signals. The delay in GPS signal induced by the ionosphere is proportional to TEC along the path from the GPS satellite to a receiver. The diurnal monthly and seasonal variations of ionospheric electron content were studied during the year 2010, a year of extreme solar minimum (F10.7\ =\ 81 solar flux unit), with data from the GPS receiver and the Digisonde Portable Sounder (DPS) collocated at Ilorin (Geog. Lat. 8.50\textdegreeN, Long. 4.50\textdegreeE, dip -7.9\textdegree). The diurnal monthly variation shows steady increases in TEC and F2-layer critical frequency (foF2) from pre-dawn minimum to afternoon maximum and then decreases after sunset. TEC show significant seasonal variation during the daytime between 0900 and 1900\ UT (LT\ =\ UT\ +\ 1\ h) with a maximum during the March equinox (about 35 TECU) and minimum during the June solstice (about 24 TECU). The GPS-TEC and foF2 values reveal a weak seasonal anomaly and equinoctial asymmetry during the daytime. The variations observed find their explanations in the amount of solar radiation and neutral gas composition. The measured TEC and foF2 values were compared with last two versions of the International Reference Ionosphere (IRI-2007 and IRI-2012) model predictions using the NeQuick and CCIR (International Radio Consultative Committee) options respectively in the model. In general, the two models give foF2 close to the experimental values, whereas significant discrepancies are found in the predictions of TEC from the models especially during the daytime. The error in height dependent thickness parameter, daytime underestimation of equatorial drift and contributions of electrons from altitudes above 2000\ km have been suggested as the possible causes.

Adebiyi, S.J.; Odeyemi, O.O.; Adimula, I.A.; Oladipo, O.A.; Ikubanni, S.O.; Adebesin, B.O.; Joshua, B.W.;

Published by: Advances in Space Research      Published on: 08/2014

YEAR: 2014     DOI: 10.1016/j.asr.2014.03.026

Equator; IRI-model; NmF2; Prediction; TEC

Ionospheric response to magnetic activity at low and mid-latitude stations

The F2-layer response to the moderate storm of 5\textendash7 April 2010 was investigated using data from two equatorial stations (Ilorin: lat. 8.5\textdegreeN, 4.5\textdegreeE; Kwajalein: lat. 9\textdegreeN, long. 167.2\textdegreeE) and mid-latitude (San Vito: lat. 40.6\textdegreeN, long. 17.8\textdegreeE; Pruhonice: lat. 50\textdegreeN, long. 14.6\textdegreeE). Before storm commencement, enhancement, and depletion of NmF2 values were observed in the equatorial and mid-latitude stations, respectively, indicating the latitudinal dependence of the pre-storm event. All the stations with the exception of Kwajalein show positive phase in NmF2 response at the storm onset stage. Positive phase in NmF2 continues over Ilorin and appears on the daytime ionosphere of Kwajalein on 6 April, whereas negative phase suppressed the positive feature in Pruhonice and San Vito until the recovery condition. The differences in the response of F2-layer to the storm for the two equatorial stations were attributed to their longitudinal differences. On the average, both theAE and D _st indices revealed poor correlation relationship. More studies are required to ascertain this finding.

Adebiyi, Shola; Adimula, Isaac; Oladipo, Olusola; Joshua, Benjamin; Adebesin, Babatunde; Ikubanni, Stephen;

Published by: Acta Geophysica      Published on: 08/2014

YEAR: 2014     DOI: 10.2478/s11600-014-0205-x

Electric field; equatorial station; Ionosphere; mid-latitude; moderate storm; positive phase