Ionospheric Disturbances during Strong Geomagnetic Storm St. Patrick on 17 March 2015

In this paper, we examine both the global and local distribution of the ionospheric response represented by Total Electron Content (TEC) for a geomagnetic storm that occurred on 17 March 2015. The behaviour of the measured TEC and median TEC data was compared to analyze in detail the recorded ionospheric disturbance. Selected energy flux data show an increase in particle precipitation in the polar latitudes of both hemispheres, which are strongest in the midnight longitudinal sector. The results of the spatial distribution of TEC response as well as the behaviour of the ionosphere at individual points show that i) in the analysis of the Northern Hemisphere as a result of the additional ionization from particle precipitation in the night hours a positive ionospheric response is observed; ii) in the region of the polar oval in both hemispheres, the dependence of the response on local time illustrates the change of the predominant mechanism of the ionospheric response; and iii) spatial distributions of median TEC and measured TEC allow for a detailed analysis of the observed effects of Equatorial Ionization Anomaly (EIA), associated with the positive anomalies observed in TEC in the equatorial region.