Limits on convective penetration from stellar cores
Abstract
The Integral Constraint on convective penetration gives an upper limit on the extent of convective penetration. If this is applied to small convective cores then the maximum extent of the penetration region is shown to be at most about 0.18 times the radius of the core independent of the details of energy generation and opacity. For larger cores the penetration distance depends on the particular properties of the nuclear reactions and opacity. Using simple power law approximations for the energy generation and opacity, the upper bound to the penetration distance is found to be approximately 0.2 of the core radius, and the core mass to be about 1.8 times the value without penetration, for a range of conditions and core sizes. The ratio of the maximum penetration distance to the scale height at the edge of the 'classical boundary' varies very strongly with core size, and modelling penetration by taking the penetration distance as a multiple of the scale height is likely to give misleading results. This is especially true for small cores such as exist in the early stages of the evolution of solar type stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1992
- Bibcode:
- 1992A&A...266..291R
- Keywords:
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- Stellar Cores;
- Stellar Evolution;
- Computational Astrophysics;
- Stellar Convection;
- Astrophysics