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Long-term (a few days) variation of magnetic helicity injection wascalculated for 28 solar active regions which produced 47 CMEs to find itsrelationships with the CME occurrence and speed using SOHO/MDI line-of-sightmagnetograms. As a result, we found that the 47 CMEs can be categorized intotwo different groups by two characteristic evolution patterns of helicityinjection in their source active regions which appeared for about 0.5-4.5 daysbefore their occurrence: (1) a monotonically increasing pattern with one signof helicity (Group A; 30 CMEs in 23 active regions) and (2) a pattern ofsignificant helicity injection followed by its sign reversal (Group B; 17 CMEsin 5 active regions). We also found that CME speed has a correlation withaverage helicity injection rate with linear correlation coefficients of 0.85and 0.63 for Group A and Group B, respectively. In addition, these two CMEgroups show different characteristics as follows: (1) the average CME speed ofGroup B (1330km/s) is much faster than that of Group A (870km/s), (2) the CMEsin Group A tend to be single events, whereas those in Group B mainly consist ofsuccessive events, and (3) flares related to the CMEs in Group B are relativelymore energetic and impulsive than those in Group A. Our findings thereforesuggest that the two CME groups have different pre-CME conditions in theirsource active regions and different CME characteristics.

The Occurrence and Speed of CMEs Related to Two Characteristic Evolution Patterns of Helicity Injection in Their Solar Source Regions