ANALYSES OF TOTAL ELECTRON CONTENT VARIATIONS OVER NORTHERN AND SOUTHERN NIGERIA

: Introduction: Total Electron Content (TEC) is a parameter of the ionosphere that produces great effect on radio signals. We present the diurnal and seasonal variations of vertical Total Electron Content (vTEC) during the ascending phase of solar cycle 24. A moderate solar activity year (2011) with sunspot number, Rz = 55.7 is used in this study. Aims: To compare the diurnal and seasonal variations of TEC at Southern and Northern Nigeria. Materials and Methods: TEC deduced from the dual frequency GPS measurements obtained at two ground stations namely: Ahmadu Bello University Zaria (ABUZ) with longitude 7.39 o E in the north and University of Nigeria Enugu (UNEC) with longitude 7.30 o E in the south are considered. Both stations are located within the same longitude and has a latitudinal difference of 4.74 o in the Nigerian equatorial ionosphere (NEI). Results: The diurnal variation of TEC shows a steep increase starting from sunrise, reaching daytime maximum between 13 – 15 LT at UNEC and 14 – 16 LT at ABUZ, then falls to a minimum at sunset. Dawn depression occurred at the same local time of 04 LT at both stations. On a seasonal scale, Pre- and post-midnight values were highest during the Equinoxes, followed by December solstice and least in June Solstice season at ABUZ. Pre- and post-midnight values were also higher during the Equinoxes than the Solstice season at UNEC, although they are about the same range. Also, TEC values are observed to be slightly higher for all hours and seasons at Enugu in the south than Zaria in the north except during March equinox at Zaria where TEC values were higher during the daytime . Conclusion: This implies that there could be little variations in TEC even within the same latitudinal zone.

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