Ionospheric Response to Two Geomagnetic Storms on 12–13 November 2025 over European Region

Abstract

The present research reveals the ionospheric response over Europe during two strong geomagnetic storms (class G5 and G3) on 12–13 November 2025. In the analysis of the manifestation of geomagnetic conditions and to describe in detail the selected geomagnetic disturbances, the Dst index was considered. The ionospheric response is represented by the variations in Total Electron Content (TEC) according to data from the vertical sounding of the ionosphere and GNSS data. Data from selected ionospheric stations located in the European region, were used, which were supplemented with analogous data from satellite measurements. This investigation used the separation of the ionospheric quantity TEC into three types: a) full TEC, which is the integral of the electron density for the entire ionosphere along a line vertical at a given point on the Earth's surface; b) bottom TEC – the electron density up to the maximum, and c) top TEC includes the electron density above the maximum region. In addition, the determination of the relative deviation of the quantity has been introduced, which allows an assessment of the influence of ionospheric anomalies resulting from the geomagnetic storm. The results of the analysis of the behaviour of the measured TEC values show a positive response in full TEC on 12 and 13 November, as well as in bottom TEC, with the least pronounced effect in top TEC. The analogous presentation of the relative deviation demonstrates the most significant influence of geomagnetic storms on top TEC. This analysis allows the response of each individual ionospheric region to be examined.