title: Dynamo efficiency controlled by hydrodynamic bistability.
abstract: Hydrodynamic and magnetic behaviors in a modified experimental setup of the von Kármán sodium flow-where one disk has been replaced by a propeller-are investigated. When the rotation frequencies of the disk and the propeller are different, we show that the fully turbulent hydrodynamic flow undergoes a global bifurcation between two configurations. The bistability of these flow configurations is associated with the dynamics of the central shear layer. The bistable flows are shown to have different dynamo efficiencies; thus for a given rotation rate of the soft-iron disk, two distinct magnetic behaviors are observed depending on the flow configuration. The hydrodynamic transition controls the magnetic field behavior, and bifurcations between high and low magnetic field branches are investigated.
authors.affiliation: Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS & Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Miralles
authors.forename: Johann
authors.initials: J
authors.lastname: Herault
authors.forename: Johann
authors.initials: J
authors.lastname: Herault
authors.affiliation: Laboratoire de Physique Statistique, École Normale Supérieure, CNRS, Université P. et M. Curie, Université Paris Diderot, Paris, France.
authors.forename: Stephan
authors.initials: S
authors.lastname: Fauve
authors.affiliation: Laboratoire de Physique Statistique, École Normale Supérieure, CNRS, Université P. et M. Curie, Université Paris Diderot, Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Gissinger
authors.affiliation: Laboratoire de Physique Statistique, École Normale Supérieure, CNRS, Université P. et M. Curie, Université Paris Diderot, Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Pétrélis
authors.affiliation: SPHYNX, Service de Physique de l'État Condensé, CNRS & CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: François
authors.initials: F
authors.lastname: Daviaud
authors.affiliation: SPHYNX, Service de Physique de l'État Condensé, CNRS & CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: Bérengère
authors.initials: B
authors.lastname: Dubrulle
authors.affiliation: Unité de Mécanique (chaire AREVA), ENSTA-ParisTech, 828 Boulevard des Marchaux, 91762 Palaiseau Cedex, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Boisson
authors.affiliation: Laboratoire des Écoulements Géophysiques et Industriels, CNRS & Université Joseph Fourier, BP 53, F-38041 Grenoble cedex 9, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Bourgoin
authors.affiliation: Institut de Recherche sur les Phénomènes Hors Équilibre, CNRS & Université d'Aix-Marseille, 49 rue F. Joliot Curie, B.P. 146 13384 Marseille cedex 13, France.
authors.forename: Gautier
authors.initials: G
authors.lastname: Verhille
authors.affiliation: Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS & Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Odier
authors.affiliation: Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS & Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Pinton
authors.affiliation: Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS & Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Plihon
mesh_terms: D003198:Computer Simulation; D004735:Energy Transfer; D057446:Hydrodynamics; D060526:Magnetic Fields; D008956:Models, Chemical; D009038:Motion; D012212:Rheology / Q000379:methods*; D012996:Solutions / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: D012996:Solutions