Turbulent compressible convection with rotation—penetration above a convection zone

Abstract

We perform Large eddy simulations of turbulent compressible convection in stellar-type convection zones by solving the Naviér-Stokes equations in three dimensions. We estimate the extent of penetration into the stable layer above a stellar-type convection zone by varying the rotation rate (Ω), the inclination of the rotation vector (θ) and the relative stability (S) of the upper stable layer The computational domain is a rectangular box in an f-plane configuration and is divided into two regions of unstable and stable stratification with the stable layer placed above the convectively unstable layer. Several models have been computed and the penetration distance into the stable layer above the convection zone is estimated by determining the position where time averaged kinetic energy flux has the first zero in the upper stable layer. The vertical grid spacing in all the model is non-uniform, and is less in the upper region so that the flows are better resolved in the region of interest. We find that the penetration distance increases as the rotation rate increases for the case when the rotation vector is aligned with the vertical axis. However, with the increase in the stability of the upper stable layer, the upward penetration distance decreases. Since we are not able to afford computations with finer resolution for all the models, we compute a number of models to see the effect of increased resolution on the upward penetration. In addition, we estimate the upper limit on the upward convective penetration from stellar convective cores.

Convective Boundary Mixing in Main-Sequence Stars: Theory and Empirical Constraints

“…Brummell et al [119] find that rotation decreases overshoot, while Dietrich and Wicht [130] find that only S affects overshoot and not rotation. Browning et al [121] studied 3D rotating core convection and found prolate penetration zones aligned with the rotation axis, which is consistent with the local box simulations of Pal et al [169] who found less penetration at the equator than at the poles. The effects of magnetism are even less studied, but convection can pump magnetic fields out of the convection zone and into CBM regions; this process was discovered by Drobyshevski and Yuferev [170] and has been observed in simulations [171,172]; magnetic pumping has been suggested as a mechanism for solar active region formation [173] and has been used to study the structure of the Sun's magnetic field below the convection zone [174].…”

Upward Overshooting in Turbulent Compressible Convection. III. Calibrate Parameters for One-dimensional Reynolds Stress Model

“…Rotation has important effect on convection and overshooting. For example, penetration depth may vary with latitudes because the Coriolis effect differs at high and low latitudes (Browning et al 2004;Pal et al 2008). In certain circumstance, vortices might appear when the Rossby number is small (Käpylä et al 2011).…”