Comparison of VTEC from GPS and IRI-2007, IRI-2012 and IRI-2016 over Sukkur Pakistan

The comparative analysis of measured and modelled Vertical Total Electron Content (VTEC) in low, mid and high latitude assists in the correction of Global Positioning System (GPS) measurements. In this study, we compare VTEC from GPS and International Reference Ionosphere (IRI) models (2007, 2012 and 2016) over mid latitude Sukkur (Lat $27.7^{\circ}~\text{N}$ , Long $68.8^{\circ}~\text{E}$ ) region in Pakistan during the final phase of the solar cycle 24 (2019–2020). We investigated the comparison in the form of ionospheric VTEC deviation during diurnal, monthly and seasonal analyses in measured and modelled values over the mid latitude region. The diurnal analysis shows that the measured VTEC in low magnetic activity days’ correlates with IRI-2016 as compared to IRI-2007 and IRI-2012. Whereas, IRI-2016 matches more than IRI-2007 and IRI-2012 in monthly values with minimum deviation. Moreover, the seasonal variations depict maximum variability in the spring season between measured and modelled VTEC over Sukkur. Similarly, maximum correlation ( $R>9.0$ ) is noted between measured and modelled VTEC in low magnetic activity days than high solar activity days, whereas the correlation is $R<9.0$ between ionosphere measured and modelled VTEC during high solar activity days in 2019–2020. All these investigations aid in correcting the ionospheric errors over low latitude Sukkur region.