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Rotating spherical Couette flow in a dipolar magnetic field: experimental study of magneto-inertial waves

Published online by Cambridge University Press:  14 May 2008

DENYS SCHMITT ,
T. ALBOUSSIÈRE ,
D. BRITO ,
P. CARDIN ,
N. GAGNIÈRE ,
D. JAULT  and
H.-C. NATAF
DENYS SCHMITT
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
T. ALBOUSSIÈRE
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
D. BRITO
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
P. CARDIN
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
N. GAGNIÈRE
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
D. JAULT
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
H.-C. NATAF
Affiliation:
Laboratoire de Géophysique Interne et Tectonophysique, CNRS-UJF, BP 53, 38041 Grenoble Cedex 9, France
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Abstract

The magnetostrophic regime, in which Lorentz and Coriolis forces are in balance, has been investigated in a rapidly rotating spherical Couette flow experiment. The spherical shell is filled with liquid sodium and permeated by a strong imposed dipolar magnetic field. Azimuthally travelling hydromagnetic waves have been put in evidence through a detailed analysis of electric potential differences measured on the outer sphere, and their properties have been determined. Several types of wave have been identified depending on the relative rotation rates of the inner and outer spheres: they differ by their dispersion relation and by their selection of azimuthal wavenumbers. In addition, these waves constitute the largest contribution to the observed fluctuations, and all of them travel in the retrograde direction in the frame of reference bound to the fluid. We identify these waves as magneto-inertial waves by virtue of the close proximity of the magnetic and inertial characteristic time scales of relevance in our experiment.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 604 , 10 June 2008 , pp. 175 - 197
Copyright
Copyright © Cambridge University Press 2008

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