Helicity transport from solar convection zone to interplanetary space

TL;DR

This paper reviews how magnetic helicity, a conserved quantity describing magnetic field topology, is generated in the solar convection zone, transported through the solar atmosphere, and released into interplanetary space, affecting solar eruptions.

Contribution

It provides a synthesis of recent observational and theoretical work on magnetic helicity transport from the solar interior to space, highlighting its role in solar eruptions and magnetic field evolution.

Findings

Magnetic helicity is conserved even during magnetic reconnection.

Helicity accumulation leads to flux rope formation and CMEs.

Interplanetary magnetic fields can carry large helicity amounts.

Abstract

Magnetic helicity is a physical quantity that describes field topology. It is also a conserved quantity as Berger in 1984 demonstrated that the total magnetic helicity is still conserved in the corona even when there is a fast magnetic reconnection. It is generally believed that solar magnetic fields, together with their helicity, are created in the convection zone by various dynamo processes. These fields and helicity are transported into the corona through solar photosphere and finally released into the interplanetary space via various processes such as coronal mass ejections (CMEs) and solar winds. Here I will give a brief review on our recent works, first on helicity observations on the photosphere and how to understand these observations via dynamo models. Mostly, I will talk about what are the possible consequences of magnetic helicity accumulation in the corona, namely, the formation of magnetic flux ropes, CMEs taking place as an unavoidable product of coronal evolution, and flux emergences as a trigger of CMEs. Finally, I will address on in what a form magnetic field in the interplanetary space would accommodate a large amount of magnetic helicity that solar dynamo processes have been continuously producing.