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M. H. Pinsonneault (Ohio State University)
I review the theoretical mechanisms for angular momentum transport in stars and the clues that can be obtained from observational data. In convective regions the overturn time scale is short compared to the stellar evolution time scale; the problem in this case is related to the angular momentum distribution enforced by turbulence and magnetic fields. In the limit where the convective and rotational velocities are of the same order of magnitude, the solar helioseismic data indicates that the rotation is independent of radius. However, I will demonstrate that explaining the existence of rapidly rotating horizontal branch stars requires constant specific angular momentum in their slowly rotating giant branch precursors. This suggests that the absolute rotation rate of the star plays a crucial role in the angular momentum distribution.
In radiative regions the three main classes of angular momentum transport mechanisms will be reviewed: hydrodynamic processes, magnetic fields, and waves. Solar data and the spindown of moderate to old stars implies that internal angular momentum transport in radiative regions is very effective over time scales of order a few hundred Myr. The spindown of young open cluster stars and the rotational properties of evolved stars, however, also imply that angular momentum transport in the radiative interior occurs over a time scale greater than or of order 100 Myr. The implications of these results for the theory are discussed, and some tests that could clarify the relative roles of each of the major classes of mechanisms will be discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: pinsonneault.1@osu.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.