Nonaxisymmetric instabilities of convection around magnetic flux tubes

Botha, Gert, Rucklidge, Alistair and Hurlburt, Neal (2007) Nonaxisymmetric instabilities of convection around magnetic flux tubes. The Astrophysical Journal Letters, 662 (1). L27-L30. ISSN 2041-8205

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Official URL: http://dx.doi.org/10.1086/519079

Abstract

On the surface of the Sun, magnetic flux elements collect in regions of converging flow, grow in field strength and become pores, which have been observed to exhibit nonaxisymmetric structure over a range of scales. Around a fully developed sunspot, as well as the fine scale of the penumbra, the moat sometimes shows clearly observable spoke-like structure at low azimuthal wavenumbers. We investigate the formation of azimuthal structure by computing the linear stability properties of fully nonlinear axisymmetric magnetoconvection, which takes the form of a central flux tube surrounded by a convecting field-free region. We find
steady and oscillatory instabilities with a preferred azimuthal wavenumber. The unstable modes are concentrated in the convecting region close to the outer edge of the flux tube. The instability is driven by convection, and is not a magnetic fluting instability.

Item Type: Article
Subjects: F300 Physics
F500 Astronomy
G900 Others in Mathematical and Computing Sciences
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Gert Botha
Date Deposited: 05 Apr 2013 10:07
Last Modified: 18 May 2017 09:08
URI: http://nrl.northumbria.ac.uk/id/eprint/11951

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