Comparison of the Empirical Ionospheric Models During Three Severe Geomagnetic Storm Occurred in 2015

The geomagnetic field acts as both the shield and the electron density regulator for the ionosphere. The effect of the geomagnetic field on the ionosphere can be examined separately for the geomagnetically quiet and disturbed days. In the current study, the performance of the ionospheric models was evaluated for three different severe geomagnetic storms periods during the year of 2015, which was in the beginning of the descending phase of the 24th solar cycle. These three storms occurred during 17-18 March, 22-23 June and 20-21 December of year 2015 in which first one expressed as St. Patrick's Day geomagnetic storm. The relationship between Total Electron Content (TEC) was measured by Global Positioning System (GPS) and evaluated with NeQuick 2, IRI 2016, IRI Plas (without any input- “IRI Plas”) and IRI Plas TEC (with TEC input- “IRI Plas TEC”) global models at three Turkey IGS station namely Ankara (39.57 N, 32.53 E), Istanbul (40.58 N, 29.05 E) and Erzurum (40.39 N, 40.42 E) investigated. The comparison was made separately for pre-storm, during storm and post-storm by using the Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) metrics and symmetric Kullback-Leibler Distance (KLD) methods. Among the empirical models, IRI Plas TEC is generally present to be better results than other models for all storm processes. It can be stated that IRI 2016 is better in the storm return phase compared to other phases of the storm.