Simultaneous response of NmF2 and GPS-TEC to storm events at Ilorin

Joshua, B.W.; Adeniyi, J.O.; Oladipo, O.A.; Doherty, Patricia H.; Adimula, I. A.; Olawepo, A.O.; Adebiyi, S.J.

doi:10.1016/j.asr.2018.03.031

Cited by 11 publications

(13 citation statements)

References 37 publications

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“…The NmF2 measurements—observed by ionosondes—in three longitudinal sectors (Figure 6a–6c) show that largest positive increase is observed in Asia, while the northern midlatitude stations of Africa (Figure 6b) and America (Figure 6c) have shown a decrease in NmF2 during the MP. Thus, both NmF2 and TEC have a positive correlation for the considered geomagnetic storm in agreement with the finding of Joshua et al (2018). Previous studies show that the positive storm effect is caused by various mechanisms (de Abreu et al, 2010; Huang, 2005; Goncharenko et al, 2007; Yuan et al, 2015; Zhang et al, 2004).…”

Section: Discussionsupporting

confidence: 92%

Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs

et al. 2020

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We present a study concerning a space weather event on 25–29 August 2018, accounting for its ionospheric and magnetic signatures at low latitudes and midlatitudes. The effects of a storm in several longitudinal sectors (Asia, Africa, America, and the Pacific) have been analyzed using various parameters such as total electron content (TEC), geomagnetic field, and column [O/N2] ratio. Positive ionospheric storms are found in all the longitudinal sectors having its maximum effects in the Asian sector, whereas the negative ionospheric storms have been observed in the summer hemisphere (Northern Hemisphere). A large decrease in [O/N2] ratio in the Northern Hemisphere is a possible cause of the observed negative storm effects. Ionospheric F2 region maximum electron density (NmF2) and TEC have shown a positive correlation during this storm. The study suggests that storm time‐generated wind does not have a uniform planetary extension and mainly affects dayside (America and Pacific) and duskside (Africa) sectors. During the space weather event, we observe an asymmetric variation of the magnetic field as a function of the longitude. On the other hand, the magnetic variations at midlatitudes are found to be symmetric in both hemispheres. A signature of the disturbance dynamo (anti‐Sq circulation) has been observed, mainly at low latitudes. We emphasize that the partial ring current (PRC), estimated by the ASYM‐H magnetic index, must also be taken into account along with the SYM‐H index for a better approximation of ionospheric currents. The study further suggests existence of several electric current cells in the ionosphere, which is consistent with the Blanc‐Richmond model.

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Section: Discussionsupporting

confidence: 92%

Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs

et al. 2020

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“…It is observed generally that while TEC and foF2 experienced more of enhancement, hmF2 show more negative effect. Readers are hereby referred to Joshua et al. (2018) for detailed description of the effects of the events on the ionosphere over Ilorin.…”

Section: Resultsmentioning

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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“…We can see that IRI2016 (STORM on) shows the best performance between the three models, while NPPDM and NPDM mainly overestimate the NmF2 during this storm event. Joshua et al [66] reported that NmF2 was more perturbed than TEC, which further stressed the importance of NmF2 in ionospheric modeling, particularly during disturbed geophysical conditions. Therefore, further research on solving this limitation of NPPDM is needed.…”

Section: Discussionmentioning

confidence: 97%

A New Empirical Model of NmF2 Based on CHAMP, GRACE, and COSMIC Radio Occultation

et al. 2019

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To facilitate F2-layer peak density (NmF2) modeling, a nonlinear polynomial model approach based on global NmF2 observational data from ionospheric radio occultation (IRO) measurements onboard the CHAMP, GRACE, and COSMIC satellites, is presented in this paper. We divided the globe into 63 slices from 80°S to 80°N according to geomagnetic latitude. A Nonlinear Polynomial Peak Density Model (NPPDM) was constructed by a multivariable least squares fitting to NmF2 measurements in each latitude slice and the dependencies of NmF2 on solar activity, geographical longitude, universal time, and day of year were described. The model was designed for quiet and moderate geomagnetic conditions (Ap ≤ 32). Using independent radio occultation data, quantitative analysis was made. The correlation coefficients between NPPDM predictions and IRO data were 0.91 in 2002 and 0.82 in 2005. The results show that NPPDM performs better than IRI2016 and Neustrelitz Peak Density Model (NPDM) under low solar activity, while it undergoes performance degradation under high solar activity. Using data from twelve ionosonde stations, the accuracy of NPPDM was found to be better than that of NPDM and comparable to that of IRI2016. Additionally, NPPDM can well simulate the variations and distributions of NmF2 and describe some ionospheric features, including the equatorial ionization anomaly, the mid-latitude trough, and the wavenumber-four longitudinal structure.

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Simultaneous response of NmF2 and GPS-TEC to storm events at Ilorin

Cited by 11 publications

References 37 publications

Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs

Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs

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

A New Empirical Model of NmF2 Based on CHAMP, GRACE, and COSMIC Radio Occultation

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