November 2003 event:: Effects on the Earth's ionosphere observed from ground-based ionosonde and GPS data

Intense late-cycle solar activity during October and November 2003 produced two strong geomagnetic storms: 28 October-5 November 2003 (October) and 1923 November 2003 (November); both reached intense geomagnetic activity levels, K-p = 9, and K-p = 8+, respectively. The October 2003 geomagnetic storm was stronger, but the effects on the Earth's ionosphere in the mid-latitude European sector were more important during the November 2003 storm. The aim of this paper is to discuss two significant effects observed on the ionosphere over the mid-latitude European sector produced by the November 2003 geomagnetic storm, using, data from ground ionosonde at Chilton (51.5 degrees N; 359.4 degrees E), Pruhonice (50.0 degrees N; 14.6 degrees E) and El Arenosillo (37.1 degrees N; 353.3 degrees E), jointly with GPS data. These effects are the presence of well developed anomalous storm E, layers observed at latitudes as low as 37 degrees N and the presence of two thin belts: one having enhanced electron content and other, depressed electron content. Both reside over the mid-latitude European evening sector.