Low-latitude ionospheric response from GPS, IRI and TIE-GCM TEC to Solar Cycle 24

In the present study inter-comparison of Total Electron Content (TEC) derived from the Global Positioning System, the International Reference Ionosphere (IRI-2016) model and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) during Solar Cycle 24 has been carried out. The short- and long-term variabilities in TEC have been assessed by using spectral, regression and statistical analysis. To ascertain the quiet-time climatology, TEC data have been used after filtering out the solar flares and geomagnetic storms effects. The present analysis exhibits a double-hump structure and clockwise hysteresis in TEC as regards Solar Cycle 24. The solar flux and TEC trend are found to be irregularly and slow during the rise and smooth and quick during the fall period of Solar Cycle 24. Seasonally, the semiannual anomaly is found to be a consistent feature for all phases of the solar cycle, while the winter anomaly seems to be facilitated with a level of solar activity during solstices. Another purpose of the present work is to investigate the performance of IRI-2016 and the TIE-GCM 2.0 models in comparison with GPS-TEC during Solar Cycle 24. Almost perfect agreement is found between observed and modeled TEC, delineating similar trends of the solar cycle, and of semiannual and seasonal variations. Nevertheless, significant biases are apparent between the observed and modeled TEC in terms of local time, seasons and phases of solar activity. Our results show the error in the model estimations in noontime TEC, which is as high as 100% in the IRI model and as low as 60% in the TIE-GCM model. Thus, in general, the IRI model overestimates the noon time TEC values, while TIE-GCM underestimates them.