## 1 Introduction
At present, GIMs are developed by eight ionospheric associate analysis centers (IAACs) under the flagship of the International GNSS Service (IGS) ionosphere working group (Iono-WG) task force by following their independent mathematical methods. The final combined IGS-GIMs are then generated by Iono-WG by assigning appropriate weightages to the individual TEC products released by IAACs. The IGS GIMs are provided in the IONEX (IONosphere map EXchange) format with a spatial resolution of 5\({}^{\circ}\) in longitude, a spatial resolution of 2.5\({}^{\circ}\) in latitude, and a temporal resolution of 2 h. Further detailed descriptions of IGS-GIM computation and validation can be found in the work of [PERSON] et al. [21]. Meanwhile, the source GIMs from the IAACs differ in temporal resolutions [22]. The IRI is a joint initiative by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) with the common goal of developing and improving the international standard for the parameters in the Earth's ionosphere [20]. The IRI provides the vertical TEC (VTEC) from a lower boundary of 60 km to a user-specific upper boundary of 2000 km that can be extrapolated up to an altitude of 10,000 km [20]. The model has been improved over time, with the latest version of the model denoted as IRI-2020 having been recently released in 2022 [23]. TEC variation near the geomagnetic equator is a major concern to space physicists because of its complex and dynamic nature. Hence, there is a need for further studies to strengthen the understanding of TEC variations over the equatorial and low latitudes in order to develop more precise ionospheric models for nowcasting and forecasting applications. The complex behavior of the TEC across the low latitudes could be due to the effect of the vertical electric field and horizontal magnetic field (E\(\times\)B drift) above the magnetic equator that results in the upliftment of plasma to higher altitudes through fountain effects, thereby transporting it away from the equator along the magnetic field tubes and producing a certain level of enhancements (equatorial ionization anomaly; EIA) around \(\pm 20^{\circ}\) of the magnetic equator [7; 24; 25]. The fountain effect is an electrodynamic lifting of the plasma that drifts upwards until the pressure and gravity forces are high enough to push the plasma back through the geomagnetic field lines to higher latitudes [26; 27]. Additionally, the level of solar activity plays a major role in producing huge disturbances to the electrodynamics of the equatorial ionosphere [28]. Several studies on TEC variations and assessments of physics-based, mathematical, and empirical ionospheric models at different latitudinal regions spanning the Euro-African, Asian and American longitudes have been presented in the past [1; 7; 20; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38]. However, there are still some lapses in terms of model assessment accuracy across the American, African and Asian longitudes that need further improvements. Additionally, there is a need for further studies to reinforce the efforts of past researchers. [PERSON] et al. [39] studied longitudinal variations in TEC and ion density over the American longitudinal sector, reporting that the TEC variation in the American longitude is larger over the east coast than the west coast and that the vertical drift and thermospheric winds control the longitudinal four-wave structure in TEC and ion density. [PERSON] et al. [40] elucidated that there are higher VTEC values in the African longitude than in the American longitude, which further increase with solar activity. They also concluded that maximum and minimum VTEC values were recorded during the March equinox and the solstices, respectively. [PERSON] et al. [41] investigated the TEC variations over the magnetic equator and EIA region in Africa, highlighting a nighttime enhancement of TEC, mostly in the equinoctial months, and a higher percentage of TEC variability during the nighttime than during the day. [PERSON] et al.