Helicity Patterns of Coronal Mass Ejection–associated Active Regions

Abstract

Coronal mass ejections (CMEs) are thought to originate from the overaccumulation of magnetic helicity. While recent studies have revealed the inability of active region (AR) fields to create enough helicity for CMEs, we have tried, on the other hand, to examine whether particular helicity patterns are retained by CME-associated ARs. Nine ARs, whose vector magnetic fields and CME-associated flares were observed at Huairou, are selected in this study. For the sampled ARs, contrary to the helicity-charging picture, we find evidence that the newly emerging flux often brings up helicity with a sign opposite to the dominant helicity of the AR. Moreover, the flare/CME initiation site is characterized by close contact with magnetic flux of the opposite helicity coinciding with observed flux cancellation. This revelation suggests that the interaction and reconnection of flux systems with opposite helicity are key elements in the magnetism of CME initiation.