PRELIMINARY APPLICATION OF FUZZY CLUSTERING IN THE FLARE-GEOMAGNETIC DISTURBANCE ANALYSES

The method of fuzzy clustering is used to study 210 geomagnetic disturbance events,which were caused by the flare associated interplanetary shock waves during the period of 1975-1983.Clustering centers,fuzzy equivalent relationships and clustering indices for three kinds of clusers (i.e.large,middle and small) are obtained.Main results are: (1) for 95 % of all flare-shock waves could cause the geomagnetic disturbances (∑Kp≥16);(2) success to failure ratio of the fuzzy-clustering prediction test is about 80% for the large geomagnetic disturbance events,which were caused by those flares with importance ≥2,lasting over hour and importance≥1,lasting over 2 hours and for those where a sudden velocity increase in the solar wind,exceeding 50km/s,were observed with at least 3 radio sources;and (3) for these large events,the variation range of the geomagnetic disturbances is very wide,from ∑Kp≥12 to ∑Kp≤54,showing that the geomagnetic effects associated with the flare-interplanetary shock waves are very complicated.