Statistical study of solar active regions that produce extremely fast coronal mass ejections

We present statistical results on the properties of the solar source regions that produced the 57 fastest (>= 1500 km s(-1)) front-side coronal mass ejections (CMEs) from 1996 June to 2007 January. The properties of these fast-CME-producing regions, 35 in total, are compared with those of all 1143 active regions (ARs) in the period studied. An automated method, based on SOHO MDI magnetic synoptic charts, is used to select and characterize the ARs. For each, a set of parameters is derived that includes the areas (positive, negative, and total, denoted A(P), A(N), and A(T), respectively), the magnetic fluxes (positive, negative, and total, F-P, F-N, and F-T), the average magnetic field strength (B-avg), a quasi elongation (e) characterizing the overall shape of the AR, the number and length of polarity inversion lines (PILs, or neutral lines, N-PIL and L-PIL, respectively), and the average and maximum magnetic gradient on the PILs (GOP(avg) and GOP(max)). Our statistical analysis shows a general trend between the scales of an AR and the likelihood of its producing a fast CME; that is, the larger the geometric size (A(T)), the larger the magnetic flux (F-T), the stronger the magnetic field (B-avg), and the more complex the magnetic configuration (N-PIL and L-PIL), the greater the possibility of producing a fast CME. When all the ARs are sorted into three evenly sized groups with low, intermediate, and high values of these parameters, we find that for all the parameters, more than 60% of extremely fast CMEs are from the high-value group. The two PIL parameters are the best indicators of fast-CME production, with more than 80% coming from the high-value group.