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Issue A&A
Volume 411, Number 3, December I 2003
Page(s) 321 - 327
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20031371



A&A 411, 321-327 (2003)
DOI: 10.1051/0004-6361:20031371

Turbulent magnetic Prandtl number and magnetic diffusivity quenching from simulations

T. A. Yousef1, A. Brandenburg2 and G. Rüdiger3

1  Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 2B, 7491 Trondheim, Norway
2  NORDITA, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
3  Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

(Received 21 February 2003 / Accepted 25 August 2003 )

Abstract
Forced turbulence simulations are used to determine the turbulent kinematic viscosity, $\nu_{\rm t}$, from the decay rate of a large scale velocity field. Likewise, the turbulent magnetic diffusivity, $\eta_{\rm t}$, is determined from the decay of a large scale magnetic field. In the kinematic regime, when the field is weak, the turbulent magnetic Prandtl number, $\nu_{\rm t}/\eta_{\rm t}$, is about unity. When the field is nonhelical, $\eta_{\rm t}$ is quenched when magnetic and kinetic energies become comparable. For helical fields the quenching is stronger and can be described by a dynamical quenching formula.


Key words: magnetohydrodynamics (MHD) -- turbulence




© ESO 2003


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