Impact of Impellers on the Axisymmetric Magnetic Mode in the VKS2 Dynamo Experiment

Journal Article · Fri Sep 05 04:00:00 EDT 2008 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.101.104501· OSTI ID:21134194

Laguerre, R ^[1]; Nore, C; Ribeiro, A ^[2]; Leorat, J ^[3]; Guermond, J -L ^[2]; Plunian, F ^[4]

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1. Universite Libre de Bruxelles, CP.231, Boulevard du Triomphe, Brussels, 1050 (Belgium)
2. Laboratoire d'Informatique pour la Mecanique et les Sciences de l'Ingenieur, CNRS, Universite Paris-Sud 11 BP 133, 91403 Orsay cedex (France)
3. Luth, Observatoire de Paris-Meudon, place Janssen, 92195-Meudon (France)
4. Universite Joseph Fourier, CNRS, Laboratoire de Geophysique Interne et de Tectonophysique, 38041 Grenoble (France)

In the von Karman Sodium 2 (VKS2) successful dynamo experiment of September 2006, the observed magnetic field showed a strong axisymmetric component, implying that nonaxisymmetric components of the flow field were acting. By modeling the induction effect of the spiraling flow between the blades of the impellers in a kinematic dynamo code, we find that the axisymmetric magnetic mode is excited. The control parameters are the magnetic Reynolds number of the mean flow, the coefficient measuring the induction effect {alpha}, and the type of boundary conditions. We show that using realistic values of {alpha}, the observed critical magnetic Reynolds number, Rm{sup c}{approx_equal}32, can be reached easily with ferromagnetic boundary conditions. We conjecture that the dynamo action achieved in this experiment may not be related to the turbulence in the bulk of the flow, but rather to the {alpha} effect induced by the impellers.

• OSTI ID: 21134194
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 10 Vol. 101; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AXIAL SYMMETRY
BOUNDARY CONDITIONS
MAGNETIC FIELDS
MAGNETIC REYNOLDS NUMBER
SIMULATION
SODIUM
TURBULENCE