Testing regional vertical total electron content maps over Europe during the 17—21 January 2005 sudden space weather event

The intense level of solar activity recorded from 16 to 23 January 2005 led to a series of events with different signatures at the Earth s ionospheric distances. Measurements of the critical frequency of the F 2 layer f o F 2 and the vertical total electron content (VTEC) are used to describe the temporal and spatial electron density distributions during this space weather event, which gives an excellent opportunity to test regional VTEC maps over Europe under such disturbed solar-terrestrial conditions. In this context, the tests used to validate the International GNSS Service (IGS) VTEC maps have been applied to assess the accuracy of the European Rutherford Appleton Laboratory (RAL) VTEC maps.