Direct Observation of the Turbulent emf and Transport of Magnetic Field in a Liquid Sodium Experiment

Type Journal Article
Names Kian Rahbarnia, Benjamin P. Brown, Mike M. Clark, Elliot J. Kaplan, Mark D. Nornberg, Alex M. Rasmus, Nicholas Zane Taylor, Cary B. Forest, Frank Jenko, Angelo Limone, Jean-Fran├žois Pinton, Nicolas Plihon, Gautier Verhille
Publication The Astrophysical Journal
Volume 759
Pages 80
Journal Abbreviation The Astrophysical Journal
Date November 1, 2012
DOI 10.1088/0004-637X/759/2/80
ISSN 0004-637X
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Abstract For the first time, we have directly measured the transport of a vector magnetic field by isotropic turbulence in a high Reynolds number liquid metal flow. In analogy with direct measurements of the turbulent Reynolds stress (turbulent viscosity) that governs momentum transport, we have measured the turbulent electromotive force (emf) by simultaneously measuring three components of velocity and magnetic fields, and computed the correlations that lead to mean-field current generation. Furthermore, we show that this turbulent emf tends to oppose and cancel out the local current, acting to increase the effective resistivity of the medium, i.e., it acts as an enhanced magnetic diffusivity. This has important implications for turbulent transport in astrophysical objects, particularly in dynamos and accretion disks.
Tags Magnetohydrodynamics: MHD, dynamo, methods: laboratory, turbulence
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