The performance analysis of global ionospheric total electron content models over Türkiye region under low solar activity conditions

Abstract

This study employs Total Electron Content (TEC) values, derived from signal delays in Global Positioning System (GPS), to monitor ionospheric activity over T & uuml;rkiye. TEC values were calculated using data from 92 GNSS stations, employing various Global Ionosphere Models (GIMs) alongside the continuously operating reference stations-T & uuml;rkiye (CORS-TR). The study period was chosen during a phase of low solar activity to minimize the influence of solar-induced ionospheric disturbances. The analysis covers the years 2019, 2020, and 2021, with TEC calculations performed using the GPS-TEC software developed by Gopi Seemala at the Institute for Scientific Research, Boston College. A comparative analysis of TEC estimates from the CODE, ESA, JPL, and IGS models yielded yearly average of Root Mean Square Error (RMSE) values of 3.957, 3.958, 5.180, and 4.344 for 2019; 3.758, 4.102, 5.391, and 4.875 for 2020; and 4.360, 4.433, 5.711, and 5.104 for 2021 respectively. The highest RMSE values were observed for the JPL model, whereas the CODE model produced the lowest RMSE values. Furthermore, the monthly averaged absolute TEC differences between the GIMs and GPS-TEC indicate a notable increase in TEC values toward 2021. This increase is likely attributed to variations in solar activity during the analysed period.