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 19-23 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° N; 359.4° E), Pruhonice (50.0° N; 14.6° E) and El Arenosillo (37.1° N; 353.3° E), jointly with GPS data. These effects are the presence of well developed anomalous storm E_s, layers observed at latitudes as low as 37° 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.