Diurnal, seasonal and solar cycle variation in total electron content and comparison with IRI-2016 model at Birnin Kebbi

Abstract

Abstract. The ionosphere is the major error source for the signals of global positioning system (GPS) satellites. In the analysis of GPS measurements, ionospheric error is assumed to be somewhat of a nuisance. The error induced by the ionosphere is proportional to the number of electrons along the line of sight (LOS) from the satellite to receiver and can be determined in order to study the diurnal, seasonal, solar cycle and spatial variations in the ionosphere during quiet and disturbed conditions. In this study, we characterize the diurnal, seasonal and solar cycle variation in observed total electron content (OBS-TEC) and compare the results with the International Reference Ionosphere (IRI-2016) model. We obtained TEC from a dual-frequency GPS receiver located at Birnin Kebbi Federal Polytechnic (BKFP) in northern Nigeria (geographic location: 12.64∘ N, 4.22∘ E; 2.68∘ N dip) for the period 2011–2014. We observed differences between the diurnal variation in OBS-TEC and the IRI-2016 model for all hours of the day except during the post-midnight hours. Slight post-noon peaks in the daytime maximum and post-sunset decrease and enhancement are observed in the diurnal variation in OBS-TEC during the equinoxes. On a seasonal scale, we observed that OBS-TEC values were higher in the equinoxes than the solstices only in 2012. However, in 2011, the September equinox and December solstice recorded a higher magnitude, followed by the March equinox, and the magnitude was lowest in the June solstice. In 2013, the December solstice magnitude was highest, followed by the equinoxes, and it was lowest in the June solstice. In 2014, the March equinox and December solstice magnitudes were higher than the September equinox and June solstice magnitude. The June solstice consistently recorded the lowest values for all the years. OBS-TEC is found to increase from 2011 to 2014, thus revealing solar cycle dependence.

Variation of Vertical Total Electron Content (TEC) Over West Africa during Geomagnetic Storms

“…The profile shows a peak Sq VTEC value of 80.0 ± 2.4 between 15 UT -17 UT (generally 2 to 4 hours after local noon). Similar observation of VTEC peak had been recorded by earlier researchers (e.g [8,1,7]. In addition, the local night time enhancement of VTEC was observed in all the stations.…”

“…It's variation (i.e seasonal, diurnal and other transient form) has significant implication for several technology dependent on it. Many authors [1,2,3,4] have determined TEC using different method. Davies and Hartman [3] did a comparison of ionospheric TEC, they made use of GPS and geostationary(GOES II) satellites data in 1994 and 1995 at Boulder (40°N, 105.2°W), Colorado.…”

“…However, the nighttime GPS TEC was higher when compared to TEC obtained using GOES II satellite data. Aghogho et al [1], studied Observed Total Electron Content (OBS-TEC) and the International Reference Ionosphere (IRI-2016) model at Birnin Kebbi in northern Nigeria during the ascending and maximum phases of solar cycle 24. Their results showed OBS-TEC and the IRI-2016 model rising from a minimum in the early hours of the day to a broad daytime maximum before falling steeply to a minimum after sunset for all years.…”

“…The temporal TEC evolution has been studied by many authors [1,2,5,6,7]. Wu et al [7] studied TEC over Taiwan using 9 observational sites covering the latitudes between 21.9° -26.2° N and the longitudes between 118.4° -121.6°E, in the Equatorial Ionization Anomaly (EIA) region from September 1996 to August 1997.…”

“…Many authors [8,1,9,10] have studied the spatial variation of TEC. Rama Rao et al [10] studied Daytime variation of TEC at the equatorial region of India and he showed a minimum of 5 TEC units and maximum of 50 TEC units.…”