The role of magnetic helicity in coronal mass ejections

We investigate the factors responsible for initiating coronal mass ejections (CMEs), specifically, the role of magnetic helicity. Using numerical simulations of the breakout model for CMEs, we show that eruption occurs at a fixed magnitude of free energy in the corona, independent of the value of helicity. Almost identical eruptions are obtained for both large and zero-helicity cases. Furthermore, the eruption can actually lead to an increase in the helicity remaining in the corona. These results argue strongly against recent models that postulate a critical helicity buildup and shedding as the determining factors for CME initiation.