Issue
EPL
Volume 82, Number 2, April 2008
Article Number 29001
Number of page(s) 5
Section Geophysics, Astronomy and Astrophysics
DOI http://dx.doi.org/10.1209/0295-5075/82/29001
Published online 07 April 2008
EPL, 82 (2008) 29001
DOI: 10.1209/0295-5075/82/29001

Effect of magnetic boundary conditions on the dynamo threshold of von Kármán swirling flows

C. Gissinger1, 2, A. Iskakov3, 4, S. Fauve1 and E. Dormy2, 3

1  Laboratoire de Physique Statistique, École Normale Supérieure CNRS - 24 rue Lhomond, F-75005 Paris, France, EU
2  Laboratoire de Radioastronomie, École Normale Supérieure CNRS - 24 rue Lhomond, F-75005 Paris, France, EU
3  Institut de Physique du Globe de Paris - Paris, France, EU
4  U.C.L.A., Physics Department - Los Angeles, CA, USA

christophe.gissinger@lps.ens.fr

received 25 February 2008; accepted in final form 26 March 2008; published April 2008
published online 7 April 2008

Abstract
We study the effect of different boundary conditions on the kinematic dynamo threshold of von Kármán type swirling flows in a cylindrical geometry. Using an analytical test flow, we model different boundary conditions: insulating walls all over the flow, effect of sodium at rest on the cylinder side boundary, effect of sodium behind the impellers, effect of impellers or side wall made of a high-magnetic-permeability material. We find that using high-magnetic-permeability boundary conditions decreases the dynamo threshold, the minimum being achieved when they are implemented all over the flow.

PACS
91.25.Cw - Origins and models of the magnetic field; dynamo theories.
47.65.-d - Magnetohydrodynamics and electrohydrodynamics.

© EPLA 2008