Performance analysis of NeQuick2 and IRI-Plas models during quiet geomagnetic and low solar activity conditions at Thanjavur equatorial location: Preliminary results

The ionosphere’s dynamic fluctuations are a persistent challenge to satellite navigation and communication. The total electron content (TEC) information from global navigation satellite system (GNSS) signals provides the status of the ionosphere for fail-safe transionospheric communication. The equatorial ionization anomaly (EIA) and equatorial plasma bubble (EPB) dominate in low latitude and equatorial ionosphere. The low solar activity's fast varying pre-reversal enhancement is low, and slow varying gravity waves can seed ionospheric disturbances. This study analyses the vertical TEC (VTEC) variations using a ground-based global positioning system (GPS) receiver at Thanjavur (10.72° N, 79.02° E), Tamil Nadu, India, for the years 2019 and 2020, with specific emphasis on the Equinox and Solstice conditions during low solar activity. The suitability of global ionospheric models such as IRI-Plas and NeQuick2 models is investigated with low solar activity GPS VTEC observations. VTEC variations are more during the Vernal Equinox compared to other seasons. The NeQuick2 model underestimates the VTEC content during the night hours and overestimates the day's evening hours regardless of the month, perhaps due to higher ITU-R coefficients. The results help us improve IRI-Plas and NeQuick prediction models' accuracy.