Magnetic Helicity Injection in Solar Active Regions Related to the CME Initiation and Speed

Magnetic helicity injection in 28 solar active regions producing 46 CMEs was investigated to find its relationship with the occurrence and speed of CMEs. The helicity injection in the active regions under investigation was calculated using full-disk 96 minute MDI magnetograms. The major findings of this study are as follows. First, the 46 CMEs are categorized into two different groups by two characteristic evolution patterns of helicity injection in their active regions: (1) a monotonically increasing of helicity accumulation (Group A; 30 CMEs in 23 active regions) and (2) significant helicity injection followed by its sign reversal (Group B; 16 CMEs in 5 active regions). Second, a fairly good correlation between the helicity injection rate and the CME speed is found for the 30 CME events in Group A. Further statistical studies, however, are needed to check whether the two characteristic helicity patterns are shown in other CME-productive active regions.