Two-step solar filament eruptions

TL;DR

This paper presents a model explaining two-step solar filament eruptions, where a flux rope temporarily stabilizes before a subsequent eruption, driven by changes in the ambient magnetic field.

Contribution

It introduces a simple two-scale magnetic field model to interpret the two-step eruptions and the metastable equilibrium of flux ropes.

Findings

The model explains failed and successful filament eruptions.

Presence of two critical heights influences eruption dynamics.

Gradual decrease of magnetic field triggers eruptions.

Abstract

Coronal mass ejections (CMEs) are closely related to eruptive filaments and usually are the continuation of the same eruptive process into the upper corona. There are failed filament eruptions when a filament decelerates and stops at some greater height in the corona. Sometimes the filament after several hours starts to rise again and develops into the successful eruption with a CME formation. We propose a simple model for the interpretation of such two-step eruptions in terms of equilibrium of a flux rope in a two-scale ambient magnetic field. The eruption is caused by a slow decrease of the holding magnetic field. The presence of two critical heights for the initiation of the flux-rope vertical instability allows the flux rope to stay after the first jump some time in a metastable equilibrium near the second critical height. If the decrease of the ambient field continues, the next eruption step follows.