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. Thus the self-consistency test and the Jason altimeter test have been used to compare such performances with the IGS and Universitat Politecnica de Catalunya global ionospheric maps. The results show discrepancies between the RAL maps and the IGS ones, which leads to significant RMS and bias values of several total electron content units. Moreover, in this work a kriging technique to improve the accuracy of any regional VTEC map is also considered, with relative improvements of the RAL VTEC maps up to more than 20% at the peak of the storm.