Reconnectionless CME eruption: putting the Aly-Sturrock conjecture to rest

TL;DR

This paper demonstrates through controlled simulations that magnetic reconnection is not essential for initiating fast coronal mass ejections, challenging previous assumptions and providing evidence for an ideal MHD instability as the trigger.

Contribution

It provides the first controlled numerical evidence that CMEs can be initiated without magnetic reconnection, using a quasi-Lagrangian simulation method.

Findings

CME can be initiated by an ideal MHD instability without reconnection.

Twisted flux ropes can escape and release magnetic energy without reconnection.

Reconnection is not a necessary trigger for fast CME eruptions.

Abstract

We demonstrate that magnetic reconnection is not necessary to initiate fast CMEs. The Aly-Sturrock conjecture states that the magnetic energy of a given force free boundary field is maximized when the field is open. This is problematic for CME initiation because it leaves little or no magnetic energy to drive the eruption, unless reconnection is present to allow some of the field to escape without opening. Thus, it has been thought that reconnection must be present to initiate CMEs. This theory has not been subject to rigorous numerical testing because conventional MHD numerical models contain numerical diffusion, which introduces uncontrolled numerical reconnection. We use a quasi-Lagrangian simulation technique to run the first controlled experiments of CME initiation in the complete lack of reconnection. We find that a flux rope confined by an arcade, when twisted beyond a critical amount, can escape to an open state, allowing some of the surrounding arcade to shrink and releasing magnetic energy from the global field. This mechanism includes a true ideal MHD instability. We conclude that reconnection is not a necessary trigger for fast CME eruptions.