Solar Magnetic Flux Ropes

TL;DR

This paper reviews the formation, stability, eruption conditions, and physical implications of solar magnetic flux ropes, emphasizing their role in coronal mass ejections and the importance of decay index in eruption prediction.

Contribution

It provides a comprehensive overview of magnetic flux ropes in the solar corona, including their formation, stability criteria, and eruption mechanisms, integrating observational and theoretical perspectives.

Findings

Flux ropes can remain stable for weeks before erupting.

Decay index is a key factor in flux rope stability and eruption.

Filaments serve as tracers for flux ropes and eruption prediction.

Abstract

The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fill the whole volume of a dark coronal cavity. The flux ropes can be in stable equilibrium in the coronal magnetic field for weeks and even months, but suddenly they loose their stability and erupt with high speed. Their transition to the unstable phase depends on the parameters of the flux rope (i.e., total electric current, twist, mass loading etc.), as well as on the properties of the ambient coronal magnetic field. One of the major governing factors is the vertical gradient of the coronal magnetic field which is estimated as decay index (n). Cold dense prominence material can be collected in the lower parts of the helical flux tubes. Filaments are therefore good tracers of the flux ropes in the corona, which become visible long before the beginning of the eruption. The perspectives of the filament eruptions and following CMEs can be estimated by the comparison of observed filament heights with calculated decay index distributions. The present paper reviews the formation of magnetic flux ropes, their stable and unstable phases, eruption conditions, and also discusses their physical implications in the solar corona.