Estimation of foF2 from GPS TEC over the South African region

• A new method of deriving foF2 from the GPS-VTEC is discussed.
• The method relies on the high correlation between foF2 and VTEC.
• The method was found to be more accurate than the IRI-2012 model.
• The method is proposed to be used over Africa in regions where ionosondes do not exist.

This paper describes a statistical method (TEC2F2) of estimating the critical frequency (foF2) values from Global Positioning System (GPS) Vertical Total Electron Content (VTEC). The method has been developed over the South African region using the available ionosonde stations; Grahamstown (33.2°S, 26.3°E), Hermanus (34.4°S, 19.2°E), Louisvale (28.5°S, 21.2°E) and Madimbo (22.4°S, 30.9°E), and nearby GPS receiver stations. The analysis of the results showed the TEC2F2 method to be more accurate at estimating the foF2 parameter over South Africa than the most commonly used International Reference Ionosphere (IRI-2012) model. On average, the TEC2F2 improves foF2 estimation by 15% (2006-2012) over the IRI-2012 model. The application of this method over the rest of Africa is proposed in order to more accurately estimate the foF2 parameter in regions where ionosondes do not exist. This is a pioneering new method that allows for the utilisation of additional resources to close the gap in ionospheric mapping over Africa.