Studying the ionospheric storms over Mediterranean area for application to the HF propagation predictions

The authors discuss selected geomagnetically disturbed periods taking into account the fact that under disturbed conditions the spatial and temporal correlations of all the F-region parameters variability is greater than during quiet times. Following this, hourly values of ground-based ionospheric data (foF2, h F, M(3000)F2 and MUF(7000)F2) have been subjected to a detailed analysis in order to determine the ionospheric storm effects in and around the Mediterranean area. The stations included are Ebro (40.82N 0.49E), Rome (41.90N 12.52E), Gibilmanna (37.59N 14.01E), Grocka (44.38N 20.46E), Bekescsaba (46.67N 21.17E), Sofia (42.68N, 22.35E) and Athens (38.00N 23.60E). For the purposes of investigating the latitudinal aspects of the problem, data from De Bilt (52.10N 5.18E), Dourbes (50.10N 4.60E) and Lindau (51.65N 10.10E) have also been analysed. Lastly, the results of the analysis are discussed in relation to the relevance of various theories in the understanding of the dynamics of ionospheric storms and to the development of ionospheric short-term prediction techniques