Generation of a magnetic field by dynamo action in a turbulent flow of liquid sodium

Romain Monchaux (1) , Michaël Berhanu (2) , Mickaël Bourgoin (3) , Marc Moulin (4) , Philippe Odier (4) , Jean-François Pinton (4) , Romain Volk (4) , Stéphan Fauve (2) , Nicolas Mordant (2) , François Pétrélis (2) , Arnaud Chiffaudel (1) , François Daviaud (1) , Bérengère Dubrulle (1) , Cécile Gasquet (1) , Louis Marié (1) , Florent Ravelet (1)

1 SPEC - UMR3680 - Service de physique de l'état condensé
2 LPS - Laboratoire de Physique Statistique de l'ENS
3 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]
4 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

We report the observation of dynamo action in the von Karman sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number R-m similar to 30. A mean magnetic field of the order of 40 G is observed 30\% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows.

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Romain Monchaux, Michaël Berhanu, Mickaël Bourgoin, Marc Moulin, Philippe Odier, et al.. Generation of a magnetic field by dynamo action in a turbulent flow of liquid sodium. Physical Review Letters, 2007, 98 (4), pp.044502. ⟨10.1103/PhysRevLett.98.044502⟩. ⟨hal-00492342⟩