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Astron. Astrophys. 344, 911-917 (1999)


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Differential rotation models for late-type dwarfs and giants

L.L. Kitchatinov 1,2 and G. Rüdiger 2

1 Institute for Solar-Terrestrial Physics, P.O. Box 4026, Irkutsk, 664033, Russia (kit@iszf.irk.ru)
2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany (lkitchatinov@aip.de; gruediger@aip.de)

Received 20 April 1998 / Accepted 9 December 1998

Abstract

A model for global circulation in outer stellar convection zones is applied to simulate the angular velocity dependence of differential rotation for two spectral classes, G2 and K5, of main-sequence dwarfs. Only the solar-type rotation laws with an increasing angular velocity from pole to equator and a relatively small rotation inhomogeneity in radius were found. Differential rotation for G2 is larger compared to K5, their angular velocities being equal. As the rotation period decreases from its solar value, the absolute value of the surface differential rotation decreases initially but changes to a slight increase for periods of several days. The meridional flow inside the convection zones is confined to thin boundary layers at the top and bottom with a typical velocity amplitude of about 10 m s-1. Also a sequence of rotation laws for evolving 2.5[FORMULA] star is produced. The predicted differential rotation is solar-like in structure and super-solar in amplitude. A comparison with observations is made and implications for dynamo theory of stellar activity are briefly discussed.

Key words: stars: activity – stars: late-type – stars: rotation

Send offprint requests to: L.L. Kitchatinov

© European Southern Observatory (ESO) 1999

Online publication: March 29, 1999

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