2006.379: Nonaxisymmetric magnetic field generation in rapidly rotating late-type stars

2006.379: D. Moss (2005) Nonaxisymmetric magnetic field generation in rapidly rotating late-type stars. Astronomy & Astrophysics, 432. pp. 249-259. ISSN 0004-6361

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DOI: DOI: 10.1051/0004-6361:20041710

Abstract

Recently the discovery of the “flip-flop” phenomenon, by which a predominant “active” longitude jumps by about 180 °, on several rapidly rotating late-type stars has directed attention to the issues surrounding the presence of large-scale nonaxisymmetric magnetic fields in these objects. Here we study nonlinear mean field dynamo models with quasi-cylindrical rotation laws, acting in spherical shells. Stable nonaxisymmetric magnetic fields are found to be generated for a range of parameters and, for certain of these models, jumps in a measure plausibly related to the position of active longitudes are found to occur. In general, nonaxisymmetric fields appear to be easier to generate in thinner dynamo-active regions. However, flip-flops appear to be stronger for intermediate thicknesses of the dynamo-active shells.

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