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Title: DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT

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.

Authors:
; ; ; ; ; ; ;  [1]; ;  [2]; ; ;  [3]
  1. Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706 (United States)
  2. Max-Planck-Institut fuer Plasmaphysik (IPP), EURATOM Association, D-85748 Garching (Germany)
  3. Laboratoire de Physique de l'Ecole Normale Superieure de Lyon, CNRS and Universite de Lyon, F-69364 Lyon (France)
Publication Date:
OSTI Identifier:
22086432
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCRETION DISKS; ASTROPHYSICS; CORRELATIONS; ELECTRIC CURRENTS; ELECTROMOTIVE FORCE; LIQUID METALS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MEAN-FIELD THEORY; REYNOLDS NUMBER; SODIUM; STRESSES; TURBULENCE; VECTORS; VELOCITY; VISCOSITY

Citation Formats

Rahbarnia, Kian, Brown, Benjamin P., Clark, Mike M., Kaplan, Elliot J., Nornberg, Mark D., Rasmus, Alex M., Taylor, Nicholas Zane, Forest, Cary B., Jenko, Frank, Limone, Angelo, Pinton, Jean-Francois, Plihon, Nicolas, and Verhille, Gautier, E-mail: kian.rahbarnia@ipp.mpg.de. DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/80.
Rahbarnia, Kian, Brown, Benjamin P., Clark, Mike M., Kaplan, Elliot J., Nornberg, Mark D., Rasmus, Alex M., Taylor, Nicholas Zane, Forest, Cary B., Jenko, Frank, Limone, Angelo, Pinton, Jean-Francois, Plihon, Nicolas, & Verhille, Gautier, E-mail: kian.rahbarnia@ipp.mpg.de. DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT. United States. doi:10.1088/0004-637X/759/2/80.
Rahbarnia, Kian, Brown, Benjamin P., Clark, Mike M., Kaplan, Elliot J., Nornberg, Mark D., Rasmus, Alex M., Taylor, Nicholas Zane, Forest, Cary B., Jenko, Frank, Limone, Angelo, Pinton, Jean-Francois, Plihon, Nicolas, and Verhille, Gautier, E-mail: kian.rahbarnia@ipp.mpg.de. Sat . "DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT". United States. doi:10.1088/0004-637X/759/2/80.
@article{osti_22086432,
title = {DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT},
author = {Rahbarnia, Kian and Brown, Benjamin P. and Clark, Mike M. and Kaplan, Elliot J. and Nornberg, Mark D. and Rasmus, Alex M. and Taylor, Nicholas Zane and Forest, Cary B. and Jenko, Frank and Limone, Angelo and Pinton, Jean-Francois and Plihon, Nicolas and Verhille, Gautier, E-mail: kian.rahbarnia@ipp.mpg.de},
abstractNote = {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.},
doi = {10.1088/0004-637X/759/2/80},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}