Scaling laws in decaying helical magnetohydrodynamic turbulence

Christensson, M, Hindmarsh, M and Brandenburg, A (2005) Scaling laws in decaying helical magnetohydrodynamic turbulence. Astronomische Nachrichten, 326 (6). pp. 393-399. ISSN 0004-6337

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We study the evolution of growth and decay laws for the magnetic field coherence length xi, energy E_M and magnetic helicity H in freely decaying 3D MHD turbulence. We show that with certain assumptions, self-similarity of the magnetic power spectrum alone implies that xi~t^{1/2}. This in turn implies that magnetic helicity decays as H~t^{-2s}, where s=(xi_{diff}/xi_H)^2, in terms of xi_{diff}, the diffusion length scale, and xi_H, a length scale defined from the helicity power spectrum. The relative magnetic helicity remains constant, implying that the magnetic energy decays as E_M~t^{-1/2-2s}. The parameter s is inversely proportional to the magnetic Reynolds number Re_M, which is constant in the self-similar regime.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Depositing User: Mark Hindmarsh
Date Deposited: 06 Feb 2012 20:34
Last Modified: 02 Apr 2012 11:21
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