Comparison of a low and a middle latitude GPS-TEC in Africa during different solar activity levels

Abstract

In this work, we compared TEC values at Libreville (a low latitude station) with Sutherland (a middle latitude station) over Africa using Global Positioning System (GPS) receivers during high solar activity (HSA), moderate solar activity (MSA) and low solar activity (LSA). Apart from our confirmation that high, moderate and low values of TEC responded well to HSA, MSA and LSA, respectively at the low and middle latitude, equatorial ionization anomaly (EIA) played significant roles as regard higher values of TEC at Libreville compared to Sutherland. Interestingly, the TEC difference between a low and middle latitude revealed how EIA is majorly responsible for the occurrence of pre-reversal enhancement (PRE) in equinoctial months at Libreville. In addition, TEC difference majorly due to EIA is inactive around pre-sunrise and sunrise hours on some days during HSA and MSA. However, it is always active on all hours in all of the days during LSA. The obliterated semi-annual signature seen during HSA of seasonal difference in TEC magnitude is significantly associated with inactive EIA around 0400 LT – 0900 LT during March equinox, September equinox and December solstice.

Keywords: Low latitude; total electron content (TEC); solar activity; equatorial ionization anomaly (EIA).