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Turbulent dynamo action in a shear flow

Lookup NU author(s): Dr Vadim Urpin


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We consider the mean electromotive force and a dynamo-generated magnetic field, taking into account the stretching of turbulent magnetic field lines by a shear flow. Calculations are performed by making use of the second-order correlation approximation. In the presence of shear, the mirror symmetry of turbulence can be broken; thus turbulent motions become suitable for the generation of a large-scale magnetic field. Regardless of the shear law, turbulence can lead to a rapid amplification of the mean magnetic field. The growth rate of the mean magnetic field depends on the length-scale: it is faster for the fields with smaller length-scale. The mechanism considered is qualitatively different from the alpha dynamo, and can generate only a magnetic field that is inhomogeneous in the direction of flow. In contrast to the alpha dynamo, this mechanism also allows the generation of two-dimensional fields. The suggested mechanism may play an important role in the generation of magnetic fields in accretion discs, galaxies and jets.

Publication metadata

Author(s): Urpin V

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 1999

Volume: 308

Issue: 3

Pages: 741-744

Print publication date: 21/09/1999

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Wiley-Blackwell Publishing Ltd.


DOI: 10.1046/j.1365-8711.1999.02738.x


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