Solar filament eruptions and their physical role in triggering Coronal Mass Ejections

TL;DR

This paper reviews observational and theoretical studies on solar filament eruptions, emphasizing that the loss-of-equilibrium or torus instability is the most effective trigger for coronal mass ejections among various proposed mechanisms.

Contribution

It provides a comprehensive discussion on different eruption mechanisms, highlighting the dominance of the torus instability in CME initiation.

Findings

Over 80% of eruptions lead to CMEs.

Torus instability is identified as the primary trigger mechanism.

Multiple mechanisms can destabilize flux ropes, but torus instability is most efficient.

Abstract

Solar filament eruptions play a crucial role in triggering coronal mass ejections (CMEs). More than 80 % of eruptions lead to a CME. This correlation has been studied extensively during the past solar cycles and the last long solar minimum. The statistics made on events occurring during the rising phase of the new solar cycle 24 is in agreement with this finding. Both filaments and CMEs have been related to twisted magnetic fields. Therefore, nearly all the MHD CME models include a twisted flux tube, called a flux rope. Either the flux rope is present long before the eruption, or it is built up by reconnection of a sheared arcade from the beginning of the eruption. In order to initiate eruptions, different mechanisms have been proposed: new emergence of flux, and/or dispersion of the external magnetic field, and/or reconnection of field lines below or above the flux rope. These mechanisms reduce the downward magnetic tension and favor the rise of the flux rope. Another mechanism is the kink instability when the configuration is twisted too much. In this paper we open a forum of discussions revisiting observational and theoretical papers to understand which mechanisms trigger the eruption. We conclude that all the above quoted mechanisms could bring the flux rope to an unstable state. However, the most efficient mechanism for CMEs is the loss-of-equilibrium or torus instability, when the flux rope has reached an unstable threshold determined by a decay index of the external magnetic field.