The connection between stellar activity cycles and magnetic field topology

See, V. and Jardine, M. and Vidotto, A. A. and Donati, J.-F. and Boro Saikia, S. and Bouvier, J. and Fares, R. and Folsom, C. P. and Gregory, S. G. and Hussain, G. and Jeffers, S. V. and Marsden, S. C. and Morin, J. and Moutou, C. and do Nascimento Jr, J. D. and Petit, P. and Waite, I. A. (2016) The connection between stellar activity cycles and magnetic field topology. Monthly Notices of the Royal Astronomical Society, 462 (4). pp. 4442-4450. ISSN 0035-8711

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Abstract

Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained form ZDI and activity cycles.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to Published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 14 Oct 2016 00:29
Last Modified: 24 Jan 2018 02:05
Uncontrolled Keywords: polarimetric; evolution; stars; magnetic fields; rotation
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1093/mnras/stw2010
URI: http://eprints.usq.edu.au/id/eprint/29842

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