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Astron. Astrophys. 335, 679-684 (1998)

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Differential rotation and meridional flow in the solar convection zone with AKA-effect

B.v. Rekowski and G. Rüdiger

Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 26 June 1997 / Accepted 1 April 1998


It makes no problem to reproduce the internal rotation of the solar convection zone known by helioseismology if (artificially) the meridional flow is ignored. Its inclusion, however, strongly reduces the latitudinal differences of the angular velocity even at the surface. The amplitude of this effect, known as the `Taylor number puzzle', depends on the unknown amplitude of the eddy viscosity. The effect in detail is described here making use of the mixing-length model of the solar convection zone by Stix & Skaley (1990). The resulting differential rotation profiles are far from the observations if indeed the free factor [FORMULA] in the eddy viscosity definition does not exceed unity.

As one of the possibilities to escape the paradox the `anisotropic kinetic alpha' (AKA)-effect is here involved into the computations. We have already shown that it should appear in formulations of the mean-field hydrodynamics in rotating density-stratified turbulent fluids at the same time with the MHD alpha-effect. Its rotational dependence, however, strongly differs from the latter hence it is concentrated to the upper part of the convection zone. Nevertheless, meridional flow and rotation law are so strongly influenced that the observed differential solar rotation can be reproduced even with realistic Taylor numbers.

Key words: hydrodynamics – Sun: interior – Sun: rotation – turbulence

Send offprint requests to: Günther Rüdiger

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© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998