Catastrophic eruption of magnetic flux rope in the corona and solar wind with and without magnetic reconnection

TL;DR

This study models solar eruptions using a flux rope catastrophe framework, demonstrating that both ideal MHD instabilities and magnetic reconnection contribute to CME dynamics, with reconnection enhancing eruption speed.

Contribution

It introduces a flux rope catastrophe model that compares eruptions with and without magnetic reconnection, revealing their combined roles in CME acceleration.

Findings

CMEs can be produced by ideal MHD catastrophe alone.

Magnetic reconnection significantly increases eruption speed.

Transition from slow to fast eruptions depends on background magnetic field strength.

Abstract

It is generally believed that the magnetic free energy accumulated in the corona serves as a main energy source for solar explosions such as coronal mass ejections (CMEs). In the framework of the flux rope catastrophe model for CMEs, the energy may be abruptly released either by an ideal magnetohydrodynamic (MHD) catastrophe, which belongs to a global magnetic topological instability of the system, or by a fast magnetic reconnection across preexisting or rapidly-developing electric current sheets. Both ways of magnetic energy release are thought to be important to CME dynamics. To disentangle their contributions, we construct a flux rope catastrophe model in the corona and solar wind and compare different cases in which we either prohibit or allow magnetic reconnection to take place across rapidly-growing current sheets during the eruption. It is demonstrated that CMEs, even fast ones, can be produced taking the ideal MHD catastrophe as the only process of magnetic energy release. Nevertheless, the eruptive speed can be significantly enhanced after magnetic reconnection sets in. In addition, a smooth transition from slow to fast eruptions is observed when increasing the strength of the background magnetic field, simply because in a stronger field there is more free magnetic energy at the catastrophic point available to be released during an eruption. This suggests that fast and slow CMEs may have an identical driving mechanism.