Electric Current Equilibrium in the Corona

TL;DR

The paper investigates the instability of a specific magnetic flux configuration in the solar corona, linking it to the onset of coronal mass ejections and observable chromospheric features.

Contribution

It demonstrates that a hyperbolic flux-tube configuration with a null point is inherently unstable, providing insights into pre-eruptive states of solar eruptions.

Findings

Hyperbolic flux-tube configurations are unstable in the corona.

Stable flux-rope equilibrium leads to specific chromospheric structures.

Separatrices in the chromosphere can indicate flux-rope stability.

Abstract

A hyperbolic flux-tube configuration containing a null point below the flux rope is considered as a pre-eruptive state of coronal mass ejections that start simultaneously with flares. We demonstrate that this configuration is unstable and cannot exist for a long time in the solar corona. The inference follows from general equilibrium conditions and from analyzing simple models of the flux-rope equilibrium. A direct consequence of the stable flux-rope equilibrium in the corona are separatrices in the horizontal-field distribution in the chromosphere. They can be recognized as specific "herring-bone structures" in a chromospheric fibril pattern.