Helicity transport in a simulated coronal mass ejection

TL;DR

This study uses simulation to analyze how magnetic helicity is transported during a coronal mass ejection, revealing that most helicity remains in the source region rather than being expelled.

Contribution

It provides new insights into the helicity transport process in CMEs, showing that the majority of helicity stays in the solar corona during eruptions.

Findings

Most helicity remains in the coronal volume during CME

The erupting flux rope carries away only minor helicity

Helicity transport is constrained by energy and current considerations

Abstract

It has been suggested that coronal mass ejections (CMEs) remove the magnetic helicity of their coronal source region from the Sun. Such removal is often regarded to be necessary due to the hemispheric sign preference of the helicity, which inhibits a simple annihilation by reconnection between volumes of opposite chirality. Here we monitor the relative magnetic helicity contained in the coronal volume of a simulated flux rope CME, as well as the upward flux of relative helicity through horizontal planes in the simulation box. The unstable and erupting flux rope carries away only a minor part of the initial relative helicity; the major part remains in the volume. This is a consequence of the requirement that the current through an expanding loop must decrease if the magnetic energy of the configuration is to decrease as the loop rises, to provide the kinetic energy of the CME.