Determining the CME Onset Mechanism

Coronal Mass Ejections (CME) are the drivers of the most destructive space weather at Earth; therefore, determining their onset mechanism is of paramount importance for both space physics understanding and space weather prediction.  Two types of models for CME onset have been proposed: an ideal instability as in the kink or torus models, or magnetic reconnection as in the breakout or tether-cutting models. These two types are distinguished by the nature of the pre-eruption filament channel that powers the CME, a twisted flux rope in the case of the ideal mechanisms and a sheared arcade in the case of reconnection.  We describe two powerful new capabilities within the Space Weather Modeling Framework (SWMF) that enable the simulation of either ideal or reconnection driven CMEs. For ideal onset, we have developed and implemented a finite-beta extension of the well-known Titov-Demoulin twisted flux rope model. We present simulations using this capability and describe its application to event studies. For reconnection-driven onset we have developed and implemented the STITCH formalism, which efficiently captures the buildup of magnetic shear along a polarity inversion line by the process of helicity condensation.  We present simulations using this capability, as well, and describe its application to event studies. Furthermore, we discuss how these capabilities within SWMF will enable the community to simulate well-observed events with both ideal and reconnection onset, and by detailed comparison with the observations, finally determine the CME onset mechanism.

This work was supported by the NSF SHINE Program and the NASA Living With a Star Program.