Pattern of the variation of the TEC extracted from the GPS, IRI 2016, IRI-Plas 2017 and NeQuick 2 over polar region, Antarctica

摘要

As a result of the complex and typical behavior of the earth's magnetic field, the high latitude ionospheric parameters (such as the Vertical Total Electron Content, VTEC) are very dynamic. Thus, this study mainly focuses on the pattern of variation of the VTEC inferred from the GPS, IRI 2016, IRI-Plas 2017 and NeQuick 2 with different height over Antarctica during 2011–2017. It has been shown that the GPS-derived (GPS VTEC) and modelled (IRI 2016, IRI-Plas 2017 and NeQuick 2) VTEC do not show significant variations in the hourly values. This shows that the solar irradiance mostly responsible for the ionization of neutral molecules in the earth's upper atmosphere does not show significant hourly variation in the region. Moreover, the GPS VTEC values are larger than the modelled values on most of the hours with the highest Root-Mean-Square Deviations, RMSD (close to 14 TECU) resulting from underestimation of the VTEC by the IRI 2016 model being observed in the March equinox in 2014. On the other hand, relatively small RMSDs (less than 1 TECU) are observed on most of the hours in using all models, demonstrating that the models’ performance is good with the NeQuick 2 model showing the best followed by the IRI-Plas 2017. Similar and smooth VTEC variation patterns are also observed in the bottom-side, topside and plasmaspheric layers during both the high and low solar activity years. This shows the TEC variation does not have significant impact on the signal propagated through the ionosphere in the polar region. Besides, the highest and lowest contributions of the TEC have been seen in the topside and plasmaspheric layers, respectively. The topside TEC contribution generally increases when the solar activity (or solar irradiance) increases; while, the plasmaspheric TEC contribution enhances when the solar activity (or solar irradiance) drops. Moreover, the largest bottom-side contribution is observed in the December solstice during 2014–2017.