Overshooting by convective settling
Overshooting by convective settling
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DOI：
10.1051/0004-6361/201321793
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发表时间：
2013-11-01
影响因子：
6.5
通讯作者：
Spruit, H. C.
中科院分区：
文献类型：
--
作者：
Andrassy, R.;Spruit, H. C.
我们研究了有对流包层的恒星中的缓慢混合过程，该过程是由向下的冷羽在对流区底部下方的沉降所驱动的。如果在表面冷却的物质中有一小部分(数量级为10(-7))在羽流中下降时保持显著的熵亏，它可以到达发生锂燃烧的深度。该模型假定羽流到达对流区底部时，具有较大的对流区对比度，计算了对流区以下由于沉降过程而产生的热响应和混合。通过假定沉降质量通量相对于熵对比度呈幂函数分布，斜率在-2附近，我们得到了与观测到的太阳锂的耗竭很好的拟合。我们发现对流沉降对对流区以下的层结影响可以忽略不计，尽管它引起的混合可以改变氦浓度的梯度。
We study a process of slow mixing in stars with convective envelopes, which is driven by the settling of cool downward plumes below the base of the convection zone. If a small fraction (of order 10(-7)) of the material cooled at the surface retains a significant entropy deficit while descending in plumes, it can reach the depth where lithium burning takes place. The model calculates the thermal response and mixing below the convection zone due to the settling process, assuming that the plumes arrive at the base of the convection zone with a broad range of entropy contrasts. We obtain a good fit to the observed lithium depletion in the Sun by assuming that the settling mass flux is distributed with respect to the entropy contrast as a power law with a slope around-2. We find convective settling to have a negligible influence on the stratification below the convection zone, although mixing induced by it could modify the gradient of helium concentration.