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Lookup NU author(s): Ashley Willis,
Professor Anvar Shukurov,
Professor Andrew Soward,
Professor Dmitry Sokoloff
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The thin-disc global asymptotics are discussed for axisymmetric mean-field dynamos with vacuum boundary conditions allowing for non-local terms arising from a finite radial component of the mean magnetic field at the disc surface. This leads to an integro-differential operator in the equation for the radial distribution of the mean magnetic field strength, Q(r) in the disc plane at a distance r from its centre; an asymptotic form of its solution at large distances from the dynamo active region is obtained. Numerical solutions of the integro-differential equation confirm that the non-local effects act similarly to an enhanced magnetic diffusion. This leads to a wider radial distribution of the eigensolution and faster propagation of magnetic fronts, compared to solutions with the radial surface field neglected. Another result of non-local effects is a slowly decaying algebraic tail of the eigenfunctions outside the dynamo active region, Q(r) ∼ r-4, which is shown to persist in non-linear solutions where α-quenching is included. The non-local nature of the solutions can affect the radial profile of the regular magnetic field in spiral galaxies and accretion discs at large distances from the centre. © 2004 Taylor and Francis Ltd.
Author(s): Willis AP, Shukurov A, Soward AM, Sokoloff D
Publication type: Article
Publication status: Published
Journal: Geophysical and Astrophysical Fluid Dynamics
Print publication date: 01/08/2004
ISSN (print): 0309-1929
ISSN (electronic): 1026-7506
Publisher: Taylor & Francis
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