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Lookup NU author(s): Professor Anvar ShukurovORCiD,
Professor Kandaswamy Subramanian
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2019 by the authors.The origin of large-scale magnetic fields, detected in some low-mass (dwarf and irregular) galaxies via polarised synchrotron emission and Faraday rotation, has remained unexplained for a long time. We suggest that mean-field dynamos can be active in galaxies of this class despite their slow rotation because their discs are relatively thick. Earlier assessments of the possibility of the mean-field dynamo action in low-mass galaxies relied on estimates applicable to thin discs, such as those in massive spiral galaxies. Using both order-of-magnitude estimates and numerical solutions, we show that the strength of differential rotation required to amplify magnetic field reduces as the aspect ratio of the galactic gas layer increases. As in a thin disc, quadrupolar magnetic fields dominate in thick discs. Thus, the origin of large-scale magnetic fields in low-mass galaxies has been clarified. This class of galaxies provides a new ground for testing our understanding of galactic magnetism.
Author(s): Bera P, Shukurov A, Subramanian K
Publication type: Article
Publication status: Published
Online publication date: 29/11/2019
Acceptance date: 26/11/2019
Date deposited: 17/02/2020
ISSN (electronic): 2075-4434
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