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Seasonal variation of quiet time TEC over West and Central African equatorial/low latitude ionosphere (2011–2014)

Akala Andrew Oke-’Ovie, Oyedokun Oluwole Johnson, Bello Damilola

Acta Geophysica

2021

Vol. 69, no. 6

2483--2495

This study investigates seasonal variation of quiet-time total electron content (TEC) over West and Central African equatorial/low-latitude ionosphere during years 2011–2014. We used TEC data obtained at five African equatorial/low-latitude GPS stations, namely; Yamoussoukro (geographic coordinates 6.87° N, 5.24° W; geomagnetic coordinates 2.84°S, 67.41°E) [Ivory Coast], Cotonou (6.37° N, 2.43° E; 3.09° S, 74.52° E) [Benin Republic], Accra (5.55° N, 0.02° W; 3.50°S, 73.13°E) [Ghana], Yaoundé (3.87°N, 11.52°E; 5.29°S, 83.13°E) [Cameroon] and Libreville (0.39°N, 9.45°E; 7.99° S, 80.84°E) [Gabon]. Diurnally, at all the stations, TEC consistently reached maximum at around 1400–1600 LT and minimum at 0600 LT. Surprisingly, contrary to the notion that on season-by-season analysis, TEC over the African equatorial/low-latitude region usually attains maximum during equinoxes, in 2011 and 2013, over West and Central African low-latitude region, TEC attained maximum values in December solstice. In 2012 and 2014, highest TEC values were recorded in equinoxes. Overall, June solstice consistently recorded the lowest values of TEC over West and Central African equatorial/low-latitude region. TEC showed solar activity dependence: highest in 2014 and lowest in 2011. TEC also showed clear evidence of higher electron density at Libreville (inner flank of the southern Equatorial Ionization Anomaly (EIA) crest) than at Yamoussoukro (EIA trough). These results would be helpful in developing new predictive models or validating the existing models for the West and Central African equatorial/low-latitude ionosphere.