The energy budget of stellar magnetic fields

See, V. and Jardine, M. and Vidotto, A. A. and Donati, J.-F. and Folsom, C. P. and Boro Saikia, S. and Bouvier, J. and Fares, R. and Gregory, S. G. and Hussain, G. and Jeffers, S. V. and Marsden, S. C. and Morin, J. and Moutou, C. and do Nascimento, J. D. and Petit, P. and Rosen, L. and Waite, I. A. (2015) The energy budget of stellar magnetic fields. Monthly Notices of the Royal Astronomical Society, 453 (4). pp. 4301-4310. ISSN 0035-8711

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Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5 M⊙. We find that the energy contained in toroidal fields has a power-law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5 M⊙ having power indices of 0.72 ± 0.08 and 1.25 ± 0.06, respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the stellar rotation period with fast rotators displaying higher latitude bands than slow rotators. The results in this paper present new constraints for future dynamo studies.

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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: 02 Jun 2016 06:06
Last Modified: 24 Jan 2018 01:47
Uncontrolled Keywords: techniques: polarimetric; stars: activity; stars: magnetic field; stars: 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/stv1925

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