6 Distribution of 62 major X-ray flares in the 22nd activity cycle

Bai (1988) examined the distribution of some active regions which produced eruptive flare during the 19th, 20th and 21st solar cycles. He found that these flares were located at some special longitudes. We also examine the longitudinal distribution of active regions that produced major flares with proton events in the 22nd solar cycle. Figure 5 shows the distribution of these active regions with major flares in the heliosphere. It is found that these active regions with major flares also tend to be located at some special longitudes.

Figure 5: Distribution of 62 > M-class X-ray flares with proton event in the 22nd activity cycle. Each point denotes an active region.

Figure 6a is the histogram used to show the number of the major flares in 30$^\circ$ longitudinal bins. We note that most of the major flares tend to occur in the longitudinal bins 15$^\circ-$45$^\circ$, 225$^\circ-$285$^\circ$and 315$^\circ-$345$^\circ$ in the northern hemisphere and bins 15$^\circ-$105$^\circ$, 165$^\circ-$225$^\circ$ and 285$^\circ$ in the southern hemisphere. Figure 6b is the histogram used to show the number of active regions in the 30$^\circ$ longitudinal bins. Solid line denotes the distribution of the active regions with "abnormal chirality'', shown as "-'' sign in Fig. 4. The dotted line denotes the distribution of the active regions with "normal chirality'', shown as "+'' in Fig. 4. We notice that in the longitudinal bins with more major flares, there are more active regions with "abnormal chirality'' (shown as shadowed regions A to F). These active regions with "normal chirality'' have their longitudinal bins preferred.

Figure 6: a) Histogram of distribution of the 62 > M-class X-ray flares in the 22nd cycle in the 30$^\circ$ longitudinal bins. b) Histogram of distribution of the active regions. Solid line denotes the active regions with "abnormal chirality'', shown as "-'' sign in Fig. 4. Dotted line denotes the active regions with "normal chirality'', showed as "+'' sign in the Fig. 4.