On the GPS TEC variability for full solar cycle and its comparison with IRI-2016 model

The long-term comparison of International Reference Ionosphere (IRI-2016) predicted total electron content (TEC) with GPS TEC has been performed over low latitude northern EIA crest region (geographic: 22.29° N, 70.74° E). The model bias for various phases of solar activity 23-24 has been investigated. The statistical analysis results show that (i) Diurnal variation of TEC predicted by the IRI-2016 model mostly overestimates GPS TEC during noon hours and underestimates at the nighttime. (ii) The seasonal comparison shows that model fits best during the summer months with the least bias. In winter, noon time overestimation by the model was found irrespective of solar activity. Further, in equinoctial months, noontime bias varies with the solar activity; i.e., the model overestimates (underestimates) the observed ionospheric variations during low (high) solar activity. (iii) GPS TEC for the high solar activity year of 2014 shows a winter anomaly prominently. The nature of the IRI-2016 model bias was assessed over a low-latitude region for more than one solar cycle in this study, which will help to further improve the model.