Estimating foF2 from GPS TEC over Islamabad and Darwin using NeQuick2 during 2011–2014

Abstract

This paper describes statistical attempts of estimating the critical frequency of the F2 layer (foF2) using Global Positioning System (GPS) Total Electron Content (TEC), with the help of electron density model NeQuick2, for monthly hourly median conditions. The stations under study are Islamabad (geog. lat: 33.66° N, long: 73.23° E, geomag. lat: 25.21° N) and Darwin (geog. lat: 12.46° S, long: 130.85° E, geomag. lat: 21.96° S) for the years 2011 to 2014. As first approximation, a linear regression analysis between ionosonde foF2 values and GPS TEC produced a regression coefficient that lies between 77% to 83% at Darwin and between 81% and 87% at Islamabad. Two methods were used for the same purpose - First, using GPS TEC and NeQuick2 slab thickness, which produced the Root Mean Square Error (RMSE) of less than 1 MHz at Islamabad, but greater than 1 MHz for Darwin. Second, using an iteration process by ingesting GPS TEC in NeQuick2 to improve foF2 such that optimum foF2 obtained by iteration process has corresponding NeQuick2 TEC, which is close to GPS one within ±5%. This provides foF2 estimation with 84% confidence over Islamabad. The results show that the attempts are inspiring for obtaining reliable foF2 from GPS TEC over Islamabad.