Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...269..581r&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 269, no. 1-2, p. 581-588.
Astronomy and Astrophysics
Astrophysics
137
Cool Stars, Dynamo Theory, Interstellar Matter, Magnetohydrodynamic Turbulence, Stellar Magnetic Fields, Magnetic Flux, Turbulence Models
Scientific paper
New determinations of the alpha effect are presented in the second-order correlation approximation with both gradients of density and turbulence intensity simultaneously involved. In our first approach the magnetic back reaction is ignored but no restrictions on the rotation rate are imposed. The density stratification as well as the turbulence intensity inhomogeneity contribute with similar power to the production of the alpha effect. The known equality of both contributions appears for fast rotation only. The previously suggested change of the sign of the alpha effect in the solar overshoot region may indeed be real. Most surprising are the results for the z-component of the alpha tensor. It is negative for slow rotation and vanishes for fast rotation. While the former case is important for galaxies, the latter one concerns the majority of cool main-sequence stars. In our second approach the magnetic feedback on the turbulence is considered which leads to the known alpha quenching. We give the complete quenching functions for all alpha coefficients for arbitrary strength of the magnetic field. We find different quenching for different components of the alpha tensor. Additionally, the quenching strongly depends on the orientation of the mean magnetic field.
Kichatinov L. L.
Ruediger Guenther
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