Field linkage and magnetic helicity density
Article
Article Title | Field linkage and magnetic helicity density |
---|---|
ERA Journal ID | 1074 |
Article Category | Article |
Authors | Lund, K. (Author), Jardine, M. (Author), Russell, A. J. B. (Author), Donati, J.-F. (Author), Fares, R. (Author), Folsom, C. P. (Author), Jeffers, S. V. (Author), Marsden, S. C. (Author), Morin, J. (Author), Petit, P. (Author) and See, V. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 502 (4), pp. 4903-4910 |
Number of Pages | 8 |
Year | 2021 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stab305 |
Web Address (URL) | https://academic.oup.com/mnras/article/502/4/4903/6129345 |
Abstract | The helicity of a magnetic field is a fundamental property that is conserved in ideal MHD. It can be explored in the stellar context by mapping large-scale magnetic fields across stellar surfaces using Zeeman-Doppler imaging. A recent study of 51 stars in the mass range 0.1-1.34 M⊙ showed that the photospheric magnetic helicity density follows a single power law when plotted against the toroidal field energy, but splits into two branches when plotted against the poloidal field energy. These two branches divide stars above and below ∼0.5 M⊙. We present here a novel method of visualizing the helicity density in terms of the linkage of the toroidal and poloidal fields that are mapped across the stellar surface. This approach allows us to classify the field linkages that provide the helicity density for stars of different masses and rotation rates. We find that stars on the lower mass branch tend to have toroidal fields that are non-axisymmetric and so link through regions of positive and negative poloidal field. A lower mass star may have the same helicity density as a higher mass star, despite having a stronger poloidal field. Lower mass stars are therefore less efficient at generating large-scale helicity. |
Keywords | methods: analytical; stars: magnetic field |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of St Andrews, United Kingdom |
University of Dundee, United Kingdom | |
University of Toulouse, France | |
United Arab Emirates University, United Arab Emirates | |
University of Gottingen, Germany | |
Centre for Astrophysics | |
University of Montpellier, France | |
University of Exeter, United Kingdom | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q703x/field-linkage-and-magnetic-helicity-density
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