Journal Article

Three-dimensional magneto-shear instabilities in the solar tachocline – II. Axisymmetric case

Paul S. Cally, Mausumi Dikpati and Peter A. Gilman

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 2, pages 891-900
Published in print December 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13934.x
Three-dimensional magneto-shear instabilities in the solar tachocline – II. Axisymmetric case

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A Boussinesq model of the development of non-axisymmetric (in particular m= 1) three-dimensional magneto-shear instabilities in the solar tachocline was presented in Paper I. However, there it was erroneously concluded that the axisymmetric (m= 0) modes are stable, and they were not discussed further. Here it is shown that, although m= 0 modes are indeed stable for broad magnetic profiles, they are strongly unstable to radial shredding (high radial wavenumber) instabilities on the poleward shoulders of toroidal magnetic bands at high field strengths (roughly 40–100 kG depending on bandwidth and latitude). These instabilities have growth rates comparable to or greater than those for tipping instabilities (m= 1) in many cases, but both are strongly stabilized by gravitational stratification characteristic of the upper radiative core. Weaker fields are m= 0 stable (though weakly m= 1 unstable), even in neutral gravitational stratification (convection zone).

Keywords: Sun: interior; Sun: magnetic fields; Sun: rotation

Journal Article.  5157 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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