ANNALS OF GEOPHYSICS, cilt.52, ss.453-458, 2009 (SCI İndekslerine Giren Dergi)
Geomagnetic Storms (GS) and Ionospheric Storms (IS) for high geomagnetic activity conditions are studied in Istanbul (IST) and in Rome (RO). Further and revised results that led to new interpretations are briefly presented here following a previous paper on the severe storm effects on the ionosphere over Istanbul. The series of storms started on 28th October 1968 and went on to 2nd November 1968 with the geomagnetic index Kp reaching Values up to 8. Deviations of the critical frequency of the F2 layer, Delta foF2(%), from monthly medians up to 100% were observed. Power spectral results Show here that not only the Diurnal Planetary Waves (PW) of 2.3 day periodicity but also tidal waves with semidiurnal (12h), teridiurnal (8h) and quaterdiurnal (6h) characteristic times are present.