EAS Publications Series
Volume 26, 2007Stellar Evolution and Seismic Tools for Asteroseismology - Diffusive Processes in Stars and Seismic Analysis
|Page(s)||49 - 64|
|Published online||20 June 2007|
C.W. Straka, Y. Lebreton and M.J.P.F.G. Monteiro (eds)
EAS Publications Series, 26 (2007) 49-64
Modeling Stellar Interiors with Rotational Mixing
LUTH, Observatoire de Paris, 92195 Meudon, France
Although it presently includes convective overshoot, microscopic diffusion, gravitational settling and radiative acceleration, the standard model of stellar structure is still unable to account for various observational facts, and there is now a large consensus that some extra mixing must occur in the radiation zones. To account for such mixing, the minimalist approach consists in introducing a parametrized turbulent diffusivity, and to adjust it so as to match the observations. A better way is to strive to implement the physical processes that may be responsible for this mixing, in particular shear-induced turbulence and large-scale meridional circulation, which both are linked with the differential rotation of the star. To describe that rotational mixing, as we call it, one has thus to follow the evolution of the internal rotation profile. By making some plausible assumptions, its is possible to reduce the advection of angular momentum through the 2-D circulation to a 1-D process, and that of the chemical elements to a vertical diffusion. It is then possible to implement these transports in a 1-D stellar evolution code. In massive stars, angular momentum is transported mainly by the meridional circulation, and there is good agreement between the observations and the predictions based on the rotational mixing. This not so for solar-type stars where another, more efficient mechanism is required to transport angular momentum. A fossil magnetic field has been invoked, but recently it has been shown that such a field would connect with the convection zone, and imprint its differential rotation on the radiation zone, which is not observed. The other candidate is the transport of angular momentum by the internal gravity waves that are emitted at the base of the convection zone; although their treatment is still somewhat crude, it appears that they can explain both the quasi-uniform rotation of the solar interior, and the depletion of lithium observed in such stars.
© EAS, EDP Sciences, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.