On the local-time variations of the storm-time TEC at European middle latitudes

Global Positioning System (GPS) measurements of the Total Electron Content (TEC) at European middle latitudes were used to obtain the TEC changes during the geomagnetic storms of the latest solar activity cycle. A common epoch analysis, with respect to geomagnetic storm onset, intensity, season, and latitude, was performed on data representing nearly 300 storm events. Results show that there is also a pronounced dependence of these TEC variations on the local time of the storm onset, as demonstrated for the location of Dourbes (50.1°N, 04.6°E).