G. Ruediger, A. Brandenburg
The electromotive force in a plane Couette flow of conducting fluids under
the influence of a large-scale magnetic field is calculated for driven
turbulence. In case of a vertically stratified intensity of the turbulence the
resulting \alpha-tensor in presence of a horizontal shear also possesses
diagonal elements known as the so-called \alpha-effect. The possibility to
measure these components is probed by both quasilinear theory and nonlinear
numerical simulations. For all magnetic Prandtl numbers <~1 we find the
\alpha-component along the flow in the high-conductivity limit exceeding the
other components. In this limit the \alpha's run linear with the magnetic
Reynolds number Rm while in the low-conductivity limit they run with the
product Rm\cdot Re. For the small magnetic Prandtl numbers of liquid sodium a
value for the electromotive force across the channel of order 0.05...0.5 mV for
magnetic fields of about 1 kGauss and velocity fluctuations of about 1 m/s is
found for a channel of (say) 50 cm height independent of its width. Such values
should be appropriate to be realized in a future laboratory experiment.
View original:
http://arxiv.org/abs/1201.0652
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