Analysis of seasonal ionospheric gradients over Turkey for year 2011

Ground Based Augmentation Systems (GBAS) monitor the ionosphere locally for giving measurement integrity information to nearby users. Monitoring systems use ionospheric threat models to calculate the integrity information and contain ionospheric gradients estimated from the ionospheric slant delays through the maximum gradient observed days. These models show only maximum gradient estimates according to the elevation angles of the satellites. In this study, ionospheric gradients are analyzed seasonally in order to give input information to the threat modeling process over Turkey. In the analysis process, developed method also shows the effects of the geomagnetic storms and earthquakes on the ionospheric gradients. As a result, for the first time, by using the developed tool, a detailed seasonal threat modeling is obtained over Turkey for year 2011. According to the analysis results, maximum gradient observed as 20 mm/km and variability of the gradients are highly dependent on to geomagnetic storms and earthquakes over Turkey in 2011. The seasons with more earthquakes and geomagnetic storms have more high gradients.