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    Analysis of global TEC prediction performance of IRI-PLAS model
    (Elsevier Sci Ltd, 2019) Alcay, Salih; Oztan, Gurkan
    The International Reference Ionosphere (IRI) empirical model provides valuable data for many fields including space and navigation applications. Since the IRI model gives the ionospheric parameters in the altitude range from 50 km to 2000 km, researchers focused on the IRI-PLAS model which is the plasmasphere extension of the IRI model. In this study, Total Electron Content (TEC) prediction performance of the IRI-PLAS model was examined at a global scale using the location of globally distributed 9 IGS stations. Besides the long term (01.01.2015-31.12.2015) behavior of the model, TEC predictions during the equinox and solstice days of 2014-2017 were also tested. IRI-PLAS-TEC values were examined in comparison with GPS-TEC data. Hourly interval of yearly profile exhibits that when the geomagnetic and solar active days are ignored, differences between IRI-PLAS-TEC and GPS-TEC are rather small (similar to 2-3 TECU) at stations in the northern hemisphere, generally similar to 4-5 TECU level at the southern hemisphere stations and reaching above 10 TECU for few hours. While the IRI-PLAS-TEC generally overestimates the GPS-TEC at southern hemisphere stations during quiet days, the model-derived TEC underestimates GPS-TEC during solar active days. IRI-PLAS-TEC and GPS-TEC values exhibit similar trend for the equinoxes 21 March and 23 September which refer equivalent conditions. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.
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    Comparison of IRI_PLAS and IRI_2012 model predictions with GPS_TEC measurements in different latitude regions
    (Ist Nazionale Di Geofisica E Vulcanologia, 2017) Alcay, Salih; Oztan, Gurkan; Selvi, Huseyin Zahit
    The International Reference Ionosphere (IRI) is an empirical model for providing ionospheric parameters, including Total Electron Content (TEC), electron density, electron and ion temperature etc., in the altitude range from 50 km to 2000 km. Since the IRI model is limited up to 2000 km, IRI_PLAS model, plasmasphere extension of the IRI model, was proposed by the researchers. This paper investigates the TEC prediction performance of IRI_PLAS and IRI_2012 models by comparing GPS TEC data, in different latitude regions for magnetically active and quiet days. TEC data over 9 International GNSS Service ( IGS) stations, located in different latitude regions, are used for the comparison. Evaluation of the diurnal results reveals good agreement with correlation coefficient >0.9 between GPS_TEC and empirical models for the quiet day irrespectively of the latitudinal data used. However, while the differences are not relatively large in most part of the active days, they reach high level, above 30 TECu, in some parts of the days.