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.

Perturbations in the solar atmosphere are the major origins of geomagnetic storms. Reconfiguration of magnetic fields in the solar atmosphere causes uplift of materials from the solar chromosphere into the corona. These relatively cool, but dense materials are suspended against gravity at greater heights by magnetic tension in the dips of the field lines, appearing by absorption against the hotter and brighter background (Carlyle, 2016). These materials could be elongated in structures, to the order of thousands of kilometers in length to form filaments, which could, in turn erupt from the solar coronal surface as Coronal Mass Ejection (CME). CMEs, particularly the Earth-directed ones are the sources of space weather events (e.g., geomagnetic storms) on the Earth. High Speed Streams (HSSs) from the Sun's coronal holes are the sources of the Corotating Interaction Regions (CIRs) which also known to cause geomagnetic storms (Burlaga & Lepping, 1977;Gosling, 1993). The occurrences of geomagnetic storms do influence the electrodynamics of

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