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arXiv · 0904.1027

Helical magnetorotational instability in a Taylor-Couette flow with strongly reduced Ekman pumping

Frank Stefani·Gunter Gerbeth·Thomas Gundrum·Rainer Hollerbach·Jānis Priede·Günther Rüdiger·Jacek Szklarski
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Abstract

The magnetorotational instability (MRI) is thought to play a key role in the formation of stars and black holes by sustaining the turbulence in hydrodynamically stable Keplerian accretion discs. In previous experiments the MRI was observed in a liquid metal Taylor-Couette flow at moderate Reynolds numbers by applying a helical magnetic field. The observation of this helical MRI (HMRI) was interfered with a significant Ekman pumping driven by solid end-caps that confined the instability only to a part of the Taylor-Couette cell. This paper describes the observation of the HMRI in an improved Taylor-Couette setup with the Ekman pumping significantly reduced by using split end-caps. The HMRI, which now spreads over the whole height of the cell, appears much sharper and in better agreement with numerical predictions. By analyzing various parameter dependencies we conclude that the observed HMRI represents a self-sustained global instability rather than a noise-sustained convective one.

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Frank Stefani, Gunter Gerbeth, Thomas Gundrum, Rainer Hollerbach, Jānis Priede, Günther Rüdiger, Jacek Szklarski. 2009-04-07. Helical magnetorotational instability in a Taylor-Couette flow with strongly reduced Ekman pumping. https://doi.org/10.1103/physreve.80.066303

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