Sean P. Matt, Olivier Do Cao, B. P. Brown, A. S. Brun
The stellar luminosity and depth of the convective envelope vary rapidly with
mass for G- and K-type main sequence stars. In order to understand how these
properties influence the convective turbulence, differential rotation, and
meridional circulation, we have carried out 3D dynamical simulations of the
interiors of rotating main sequence stars, using the anelastic spherical
harmonic (ASH) code. The stars in our simulations have masses of 0.5, 0.7, 0.9,
and 1.1 M_sun, corresponding to spectral types K7 through G0, and rotate at the
same angular speed as the sun. We identify several trends of convection zone
properties with stellar mass, exhibited by the simulations. The convective
velocities, temperature contrast between up- and down-flows, and meridional
circulation velocities all increase with stellar luminosity. As a consequence
of the trend in convective velocity, the Rossby number (at a fixed rotation
rate) increases and the convective turnover timescales decrease significantly
with increasing stellar mass. The 3 lowest mass cases exhibit solar-like
differential rotation, in a sense that they show a maximum rotation at the
equator and minimum at higher latitudes, but the 1.1 M_sun case exhibits
anti-solar rotation. At low mass, the meridional circulation is multi-cellular
and aligned with the rotation axis; as the mass increases, the circulation
pattern tends toward a unicellular structure covering each hemisphere in the
convection zone.
View original:
http://arxiv.org/abs/1111.5585
No comments:
Post a Comment