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Scaling laws in decaying helical magnetohydrodynamic turbulence
journal contribution
posted on 2023-06-08, 06:51 authored by M Christensson, Mark HindmarshMark Hindmarsh, A BrandenburgWe 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.
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Publication status
- Published
Journal
Astronomische NachrichtenISSN
0004-6337External DOI
Issue
6Volume
326Page range
393-399Department affiliated with
- Physics and Astronomy Publications
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- No
Peer reviewed?
- Yes
Legacy Posted Date
2012-02-06Usage metrics
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