IRI and GPS TEC Variations over Ilorin, Nigeria

Abstract

Diurnal and day-to-day variations of vertical total electron content (VTEC) over an equatorial region (Ilorin, Nigeria; geographic 8.50°N, 4.55°E; geomagnetic 10.60°N, 78.41°E) is presented in this paper using data from the IRI model and from the AFRL-SCINDA (Air Force Research Laboratory – Scintillation Network Decision Aid) GPS receiver installed at the Ilorin station. A comparison between VTEC data from the two sources is also presented since a major concern in the work is to use available GPS-TEC data for the year 2010 to evaluate the performance of the IRI model in TEC prediction over the region, and to therefore inform a proposed use of the IRI model in TEC modeling over the African region. Our results show generally good comparisons between the IRI TEC predictions and the GPS TEC measurements, results from the comparisons on diurnal basis were, as expected, better than those on day-to-day basis. The work also indicates that the lower TEC thresholds of the IRI predictions for the days observed occurred at around 04:00 UT while for the GPS measurements they occurred at around 05:00 UT.

Keywords: GPS TEC, IRI TEC, Ilorin ionosphere, Nigeria, AFRL-SCINDA GPS