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2012ApJ...759...80R
Direct Observation of the Turbulent emf and Transport of Magnetic Field in a Liquid Sodium Experiment
Rahbarnia, Kian ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ; Current address: Max-Planck-Institut für Plasmaphysik, Wendelsteinstr. 1, D-17491 Greifswald, Germany.; ); Brown, Benjamin P. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Clark, Mike M. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Kaplan, Elliot J. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Nornberg, Mark D. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Rasmus, Alex M. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Zane Taylor, Nicholas ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Forest, Cary B. ( Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USA ; Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, USA ); Jenko, Frank ( Max-Planck-Institut für Plasmaphysik (IPP), EURATOM Association, D-85748 Garching, Germany ); Limone, Angelo ( Max-Planck-Institut für Plasmaphysik (IPP), EURATOM Association, D-85748 Garching, Germany ); Pinton, Jean-François ( Laboratoire de Physique de l'École Normale Supérieure de Lyon, CNRS & Université de Lyon, F-69364 Lyon, France ); Plihon, Nicolas ( Laboratoire de Physique de l'École Normale Supérieure de Lyon, CNRS & Université de Lyon, F-69364 Lyon, France ); Verhille, Gautier ( Laboratoire de Physique de l'École Normale Supérieure de Lyon, CNRS & Université de Lyon, F-69364 Lyon, France ) and 3 coauthors show affiliations
The Astrophysical Journal, Volume 759, Issue 2, article id. 80, 6 pp. (2012).
Published in Nov 2012
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.
Keywords:
Free Keywords: dynamo; magnetohydrodynamics: MHD; methods: laboratory; turbulence
Astronomy: dynamo; magnetohydrodynamics: MHD; methods: laboratory; turbulence
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