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Bistability between a stationary and an oscillatory dynamo in a turbulent flow of liquid sodium

Abstract : We report the first experimental observation of a bistable dynamo regime. A turbulent flow of liquid sodium is generated between two disks ill the von karman geometry (VKS experiment). When one disk is kept at rest, bistability is observed between a stationary and an oscillatory magnetic field. The stationary and oscillatory branches occur in the vicinity of a codimension-two bifurcation that results from the coupling between two modes of magnetic field. We present an experimental study or the two regimes and study in detail the region of bistability that we understand ill terms of dynamical system theory. Despite the very turbulent nature of the flow, the bifurcations of the magnetic field are correctly described by a low-dimensional model. In addition, the different regimes are robust; i.e. turbulent fluctuations do not drive any transition between the oscillatory and stationary states in the region of bistability.
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Contributor : Mickaël Bourgoin Connect in order to contact the contributor
Submitted on : Tuesday, June 15, 2010 - 2:58:37 PM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM
Long-term archiving on: : Wednesday, September 15, 2010 - 8:34:31 PM

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Mickaël Bourgoin, Michaël Berhanu, Basile Gallet, Romain Monchaux, Philippe Odier, et al.. Bistability between a stationary and an oscillatory dynamo in a turbulent flow of liquid sodium. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2009, 641, pp.217-226. ⟨10.1017/S0022112009991996⟩. ⟨hal-00492247⟩

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