HAL : hal-00016011, version 1

arXiv : physics/0512217

Code IRD Horizon : PAR00003030

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Experimental study of super-rotation in a magnetostrophic spherical Couette flow

Henri-Claude Nataf 1, Thierry Alboussière 1, Daniel Brito 1, Philippe Cardin 1, Nadège Gagnière 1, Dominique Jault 1, Jean-Paul Masson 1, Denys Schmitt 1

(16/12/2005)

We report measurements of electric potentials at the surface of a spherical container of liquid sodium in which a magnetized inner core is differentially rotating. The azimuthal angular velocities inferred from these potentials reveal a strong super-rotation of the liquid sodium in the equatorial region, for small differential rotation. Super-rotation was observed in numerical simulations by Dormy et al. [1]. We find that the latitudinal variation of the electric potentials in our experiments differs markedly from the predictions of a similar numerical model, suggesting that some of the assumptions used in the model - steadiness, equatorial symmetry, and linear treatment for the evolution of both the magnetic and velocity fields - are violated in the experiments. In addition, radial velocity measurements, using ultrasonic Doppler velocimetry, provide evidence of oscillatory motion near the outer sphere at low latitude: it is viewed as the signature of an instability of the super-rotating region.

1 :	Laboratoire de géophysique interne et tectonophysique (LGIT)
	CNRS : UMR5559 – IRD – LCPC – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I

Domaine

:

Physique/Physique/Géophysique Planète et Univers/Sciences de la Terre/Géophysique

Mots Clés : Spherical Couette flow – super-rotation – magnetostrophic – liquid sodium experiment – Hartmann layers – ultrasonic Doppler velocimetry

hal-00016011, version 1

http://hal.archives-ouvertes.fr/hal-00016011

oai:hal.archives-ouvertes.fr:hal-00016011

Contributeur : Henri-Claude Nataf <>

Soumis le : Jeudi 22 Décembre 2005, 15:00:56

Dernière modification le : Jeudi 22 Décembre 2005, 15:00:56