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

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 hydromagne...

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Bibliographic Details
Published in:Journal of fluid mechanics 2008-06, Vol.604, p.175-197
Main Authors: SCHMITT, DENYS, ALBOUSSIÈRE, T., BRITO, D., CARDIN, P., GAGNIÈRE, N., JAULT, D., NATAF, H.-C.
Format: Article
Language:English
Subjects:
Earth Sciences
Earth, ocean, space
Electric potential
Exact sciences and technology
Experiments
Fluid Dynamics
Geophysics
Geophysics: general, magnetic, electric and thermic methods and properties
Internal geophysics
Magnetic fields
Physics
Sciences of the Universe
Time
Waves
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Summary: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.
ISSN:0022-1120
1469-7645
DOI:10.1017/S0022112008001298