On the relationship between flux emergence and CME initiation

We present in this paper a statistical study aimed at understanding the possible relationship between surface magnetic field variation and CME initiation. The three samples studied comprise 189 CME-source regions, 46 active regions, and 15 newly emerging active regions. Both large-scale and small-scale variations of longitudinal magnetic fields of these regions are studied. To quantitatively study these variations, three physical quantities are calculated: the average total magnetic flux (ATF), the flux variation rate (FVR), and the normalized flux variation rate (NFVR). Our results show that 60% of the CME-source regions are found to have magnetic flux increases during 12 hours before CME eruptions and 40% are found to have magnetic flux decreases. The NFVR of CME-source regions are found to be statistically identical to those of active regions, averaged over 111 hours, and significantly smaller than those of newly emerging active regions. In addition 91% of the CME-source regions are found to have small-scale flux emergence, whereas small-scale flux emergences are also easily identified in active regions during periods with no solar surface activity. Our study suggests that the relationship between flux emergence and CME eruption is complex and the appearance of flux emergence alone is not unique for the initiation of CME eruption.