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Issue A&A
Volume 397, Number 2, January II 2003
Page(s) 393 - 399
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20021568



A&A 397, 393-399 (2003)
DOI: 10.1051/0004-6361:20021568

Numerical simulations of kinematic dynamo action

V. Archontis1, S. B. F. Dorch2, 3 and Å. Nordlund3

1  Instituto de Astrofisica de Canarias, Via Lactea s/n, 38200 La Laguna, Spain
2  The Institute for Solar Physics of the Royal Swedish Academy of Sciences, SCFAB, 10691 Stockholm, Sweden
3  The Niels Bohr Institute for Astronomy, Physics and Geophysics, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

(Received 2 May 2002 / Accepted 21 October 2002)

Abstract
Numerical simulations of kinematic dynamo action in steady and three-dimensional ABC flows are presented with special focus on the difference in growth rates between cases with single and multiple periods of the prescribed velocity field. It is found that the difference in growth rate (apart from a trivial factor stemming from a scaling of the rate of strain with the wavenumber of the velocity field) is due to differences in the recycling of the weakest part of the magnetic field. The single wavelength classical ABC-flow experiments impose stronger symmetry requirements, which results in a suppression of the growth rate. The experiments with larger wave number achieve growth rates that are more compatible with the turn-over time scale by breaking the symmetry of the resulting dynamo-generated magnetic field. Differences in topology in cases with and without stagnation points in the imposed velocity field are also investigated, and it is found that the cigar-like structures that develop in the classical A=B=C dynamos are replaced by ribbon structures in cases where the flow is without stagnation points.


Key words: diffusion -- magnetic fields -- magnetohydrodynamics (MHD) -- turbulence -- plasmas

Offprint request: V .D. Archontis, vasilis@ll.iac.es




© ESO 2003


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