Numerical Study of Dynamo Action at Low Magnetic Prandtl Numbers

Y. Ponty, P. D. Mininni, D. C. Montgomery, J.-F. Pinton, H. Politano, and A. Pouquet
Phys. Rev. Lett. 94, 164502 – Published 27 April 2005

Abstract

We present a three-pronged numerical approach to the dynamo problem at low magnetic Prandtl numbers PM. The difficulty of resolving a large range of scales is circumvented by combining direct numerical simulations, a Lagrangian-averaged model and large-eddy simulations. The flow is generated by the Taylor-Green forcing; it combines a well defined structure at large scales and turbulent fluctuations at small scales. Our main findings are (i) dynamos are observed from PM=1 down to PM=102, (ii) the critical magnetic Reynolds number increases sharply with PM1 as turbulence sets in and then it saturates, and (iii) in the linear growth phase, unstable magnetic modes move to smaller scales as PM is decreased. Then the dynamo grows at large scales and modifies the turbulent velocity fluctuations.

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  • Received 7 October 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.164502

©2005 American Physical Society

Authors & Affiliations

Y. Ponty1, P. D. Mininni2, D. C. Montgomery3, J.-F. Pinton4, H. Politano1, and A. Pouquet2

  • 1CNRS UMR6202, Laboratoire Cassiopée, Observatoire de la Côte d’Azur, BP 4229, Nice Cedex 04, France
  • 2ASP/NCAR, P.O. Box 3000, Boulder, Colorado 80307-3000, USA
  • 3Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA
  • 4CNRS UMR5672, Laboratoire de Physique, École Normale Supérieure de Lyon, 46 Allée d’Italie, 69007 Lyon, France

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Issue

Vol. 94, Iss. 16 — 29 April 2005

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