GPS Satellite Signals Derived Ionospheric TEC and Assessment of IRI-2016 and SPIM-2017 Model Predictions over Indian Region

Apart from the primary intention of positioning, navigation and timing applications, the global positioning system (GPS) has been popularized in providing the estimates of ionospheric total electron content (TEC) that is confirmed to be the reason for ionospheric error degrading the accuracy of above applications. In the present study, we investigated the variation of GPS-TEC over the Indian low latitudes during the period 2012 to 2015 constituting midst of solar cycle-24. The results are further compared with the global ionosphere maps (GIMs), international reference ionosphere (IRI-2016) and standard plasmasphere-ionosphere model (SPIM-2017) to evaluate the model performances over the region. Observation during the typical geomagnetically quiet period (26-28 March 2013) demonstrates clear increase in TEC from equator to anomaly crest and declines thereafter towards higher latitudes. Seasonal comparisons confirm higher TEC magnitudes during equinox than the solstice seasons. Also, studies during geomagnetically disturbed period shows relatively poorer performances of the models during the episode of storms. In general, IRI-2016 model estimates seems to be manifesting closer values to the observed GPS-TEC; however with data ingested from IGS-GIMs into the SPIM-2017 model the estimations appears to be more realistic among all. Further improvements are suggested in the existing model for relatively better accuracy of TEC estimations and mitigation of ionospheric errors in communication and navigation signals over the low latitude Indian region.