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Discussion papers | Copyright
https://doi.org/10.5194/angeo-2018-57
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 08 Jun 2018

Regular paper | 08 Jun 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).

Morphology of GPS and DPS-TEC Over an Equatorial Station: Validation of IRI and NeQuick 2 Models

Olumide O. Odeyemi1, Jacob Adeniyi2, Olushola Oladipo3, Olayinka Olawepo3, Isaac Adimula3, and Elijah Oyeyemi1 Olumide O. Odeyemi et al.
  • 1Department of Physics, University of Lagos, Nigeria
  • 2Department of Physical Sciences, Landmark University, Omu-Aran, Nigeria
  • 3Physics Department, University of Ilorin, Ilorin

Abstract. We investigated total electron content (TEC) at Ilorin (8.50°N 4.65°E, dip lat. 2.95) during a low solar activity 2010. The investigation involved the use of GPS derived TEC, TEC estimated from digisonde portable sounder data (DPS-TEC), the International Reference Ionosphere model (IRI-TEC) and NeQuick 2 model (NeQ-TEC). The five most quietest days of the months obtained from the international quiet days (IQD) from the website http://www.ga.gov.au/oracle/geomag/iqd_form.jsp were used for the investigation. During the sunrise period, we found that the rate of increases in DPS-TEC, IRI-TEC and NeQ-TEC were higher with respect to GPS-TEC. One reason for this can be alluded to an overestimation of plasmaspheric electron content (PEC) contribution in modeled TEC and DPS-TEC. A correction factor around the sunrise where a significant percentage difference of overestimations between the modeled TEC and GPS-TEC was obtained 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 predicts TEC very well. The lowest discrepancies were observed in May, June and July (June solstice) between the observed and all the model values in 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 ~1000km 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 NeQ model profile whereas the exaggeration of PEC contribution in IRI-TEC amount to overestimations of GPS-TEC. The excess bite-out observed in DPS-TEC and NeQ-TEC show the indication of overprediction of fountain effect in these models. Therefore, the daytime bite-out observed in these two models require a modifier that could moderate the perceived fountain effect morphology in the models accordingly. Seasonally, we found that all the TECs maximize and minimize during the March equinox and June solstice, respectively. Therefore, GPS-, DPS-, IRI- and NeQ-TEC reveal the semi-annual variations in TEC as reported in all regions. 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 highest percentage difference recorded especially for DPS-TEC and the models in March, and November and December for DPS-TEC.

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Short summary
This paper investigates the combined relationship between the GPS-TEC and DPS-TEC, and validations of IRI-TEC, and NeQ-TEC models. Our findings reveal the suitability of DPS-TEC, IRI-TEC and NeQ-TEC in place of GPS-TEC. The DPS-TEC predict GPS-TEC very well during the daytime when PEC contribution is often negligible, however, the dusk period requires a substantial correction. Thus, the changed TEC obtained could be used to improve models for the equatorial station in Africa.
This paper investigates the combined relationship between the GPS-TEC and DPS-TEC, and...
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