Interpreting magnetic helicity flux in solar flux emergence

Prior, C; MacTaggart, D

Abstract

Magnetic helicity flux gives information about the topology of a magnetic field passing through a boundary. In solar physics applications, this boundary is the photosphere and magnetic helicity flux has become an important quantity in analysing magnetic fields emerging into the solar atmosphere. In this work we investigate the evolution of magnetic helicity flux in magnetohydrodynamic (MHD) simulations of solar flux emergence. We consider emerging magnetic fields with different topologies and investigate how the magnetic helicity flux patterns correspond to the dynamics of emergence. To investigate how the helicity input is connected to the emergence process, we consider two forms of the helicity flux. The first is the standard form giving topological information weighted by magnetic flux. The second form represents the net winding and can be interpreted as the standard helicity flux less the magnetic flux. Both quantities provide important and distinct information about the structure of the emerging field and these quantities differ significantly for mixed sign helicity fields. A novel aspect of this study is that we account for the varying morphology of the photosphere due to the motion of the dense plasma lifted into the chromosphere. Our results will prove useful for the interpretation of magnetic helicity flux maps in solar observations.

Citation

Prior, C., & MacTaggart, D. (2019). Interpreting magnetic helicity flux in solar flux emergence. Journal of Plasma Physics, 85(2), Article 775850201. https://doi.org/10.1017/s0022377819000229

• Journal Article Type: Article
• Acceptance Date: Feb 6, 2019
• Online Publication Date: Mar 18, 2019
• Publication Date: Apr 30, 2019
• Deposit Date: Feb 21, 2019
• Publicly Available Date: Sep 19, 2019
• Journal: Journal of Plasma Physics
• Print ISSN: 0022-3778
• Electronic ISSN: 1469-7807
• Publisher: Cambridge University Press
• Peer Reviewed: Peer Reviewed
• Volume: 85
• Issue: 2
• Article Number: 775850201
• DOI: https://doi.org/10.1017/s0022377819000229
• Public URL: https://durham-repository.worktribe.com/output/1337086