Progress In Electromagnetics Research C, Vol. 114, 279–295, 2021 Performance Evaluation of Global Ionospheric Models with Indian Regional Navigation Data over Low Latitude Station during Low Solar Activity Year 2017 Devireddy Kavitha * and Perumalla Naveen Kumar Abstract—This paper discusses the variation of ionospheric Total Electron Content (TEC) over low latitude Indian region, Hyderabad station (Lat: 17.39 ◦ N, Lon: 78.31 ◦ E) for geomagnetic quiet and disturbed days during the low solar activity period (2017 year) of the 24th solar cycle using global ionospheric models and experimental NavIC (Navigation with Indian Constellation) data. The work mainly focuses on the performance of the IRI Plas 2017 (International Reference Ionosphere) model with and without assimilation of TEC input, GIM TEC (Global Ionospheric Maps) and IRI 2016 models. In order to evaluate the performance of the models, the diurnal, monthly, and seasonal variations of Vertical TEC (VTEC) are predicted and compared with Indian regional NavIC data. From the result analysis it is observed that smaller Root Mean Square Errors (RMSEs) between NavIC VTEC and modelled VTEC are found in June and December solstice months than March and September equinox months. The VTEC predicted by the IRI Plas with assimilation of TEC input option produced smaller estimation errors than IRI Plas without assimilation of TEC input and IRI 2016 model. The same analysis has been tested for geomagnetic storm occurred during 7–9 September, 2017 for different locations. The IRI Plas 2017 with TEC input option exhibits better performance than IRI Plas and IRI 2016 models. Therefore, the VTEC predictions by assimilation of optional inputs will be helpful in applications of ionspheric studies to predict the dynamics in the ionosphere particularly for the period of disturbed geomagnetic conditions. 1. INTRODUCTION The NavIC/IRNSS (Indian Regional Navigation Satellite System) with 7 satellites constellation was developed by Indian Space Research Organization (ISRO). The NavIC system covers India and a range of 1,500 km beyond its borders. It can provide position accuracy within 10 m over the Indian landmass and less than 20 m over the oceans. It is expected to provide better coverage area and improved accuracy with satellite constellation enhanced to 11 satellites. In the present constellation four satellites are geosynchronous (1A, 1B, 1D, 1E), and the remaining is geostationary (1C, 1F, 1G). The IRNSS satellites are placed in the orbits at the height of 36,000 km from the earth. The NavIC operates in L5 (1176.45 MHz) and S1 (2492.028 MHz) frequencies [1]. Any regional or global navigation system performance is degraded by several sources of errors such as satellite orbital error, clock error, multipath effects, satellite and receiver biasing, Dilution of Precision, tropospheric error, and ionospheric error. Among them ionospheric error is the predominant source of error. This error is directly proportional to the TEC present in the ionosphere. The ionospheric propagation effects play a critical role on the performance of Communication, Navigation, and Surveillance (CNS) system applications. Precise Received 31 May 2021, Accepted 13 August 2021, Scheduled 26 August 2021 * Corresponding author: Devireddy Kavitha (kavithadevireddy@osmania.ac.in). The authors are with the Advanced GNSS Research Laboratory, Department of Electronics and Communication Engineering, Osmania University, Hyderabad, TS, India.