Ionospheric spatial and temporal variations during the 29-31 October 2003 storm

A prominent large-scale ionospheric disturbance was observed in the European mid-latitude sector during the recent extreme space weather event in October 2003. Measurements of the horizontal component of the geomagnetic field H, the critical frequency of the F2 layer foF2, and the vertical total electron content (TEC) from the European network of observational sites are used to describe the temporal and spatial storm evolution process. It is found that the ionospheric F region storm morphology was dominated by negative disturbances over high mid-latitudes and positive disturbance at low mid-latitudes during the initial phase and by overall negative disturbances during the main phase. Although a good agreement between the two independent measurements was detected by comparing the storm-time behaviour of foF2 and TEC during the main phase of the storm, some irregularities have been recognised in TEC variations at high mid-latitudes. The relative merit of real-time observational solar-terrestrial data for accurate specification of the geomagnetically disturbed ionospheric F region during the extreme space weather conditions is discussed.