Comparison of Performance of the IRI 2016, IRI-Plas 2017, and NeQuick 2 Models During Different Solar Activity (2013-2018) Years Over South American Sector

This study mainly focuses on the prediction of the variability of the vertical total electron content (VTEC) and validation of the new versions of the International Reference Ionosphere (IRI 2016), IRI extended to the plasmasphere (IRI-Plas 2017), and NeQuick 2 models over the equatorial anomaly region during 2013-2018. The Global Positioning System (GPS)-derived VTEC data inferred from the South American equatorial region during the relatively high (2013-2014), descending (2015-2016), and low (2017-2018) solar activity years have been considered as measurements to validate the models. The modeled (IRI 2016, IRI-Plas 2017, and NeQuick 2) VTEC values are generally larger than the GPS-derived VTEC values, with the highest overestimation being illustrated by the IRI-Plas 2017 model. Small underestimations are also observed in employing the IRI 2016 and NeQuick 2 models, especially when the solar activity increases. The highest root-mean-square Deviations (RMSDs) reaching up to 10 TEC units (TECU) is observed in some hours while using the IRI-Plas 2017 model during the high solar activity years. RMSDs less than 5 TECU are also observed on most of the hours while utilizing the model during all solar activity years. However, RMSD values less than 2 TECU (while using the NeQuick 2 model) and less than 1 TECU (while using the IRI 2016 model) are seen on most of the hours during 2013-2018. This shows that the performance of the IRI 2016 and NeQuick 2 is better than the IRI-Plas 2017 with the IRI 2016 model consistently revealing the best in all solar activity years.