Liquid metal experiments on helical MRI


Liquid metal experiments on helical MRI

Stefani, F.

The magnetorotational instability (MRI) plays a key role in the formation of stars and black holes. By destabilizing hydrodynamically stable Keplerian flows, the MRI triggers turbulence and enables outward transport of angular momentum in accretion discs. The Potsdam Rossendorf Magnetic InStability Experiment (PROMISE) is devoted to the experimental study of the so-called helical MRI. Preliminary experiments had confirmed the prediction that combined axial and azimuthal magnetic fields allow the investigation of the MRI in liquid metal Taylor-Couette flows at moderate Reynolds and Hartmann numbers. A drawback of these experiments was that the travelling MRI wave ceased at the radial jet that results from the Ekman pumping at the end-caps of the Taylor-Couette cell. However, by using split end-caps the Ekman pumping is strongly reduced so that the MRI wave can travel freely through the entire height. Consequently, the transition to MRI appears much sharper and in improved agreement with numerical predictions. By analyzing various parameter dependencies of the MRI wave we conclude that it represents a global instability and not a noise-triggered convective one.

  • Invited lecture (Conferences)
    The Astrophysics of the Magnetorotational Instability and Related Processes, 14.-18.04.2009, Tegernsee, Germany

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Publ.-Id: 12703