Korre Lydia, Featherstone Nicholas A
Laboratory for Atmospheric and Space Physics, Boulder, CO 80303, USA.
Southwest Research Institute, Department of the Space Studies, Boulder, CO 80302, USA.
Astrophys J. 2021 Dec 10;923(1). doi: 10.3847/1538-4357/ac2dea.
Overshooting of turbulent motions from convective regions into adjacent stably stratified zones plays a significant role in stellar interior dynamics, as this process may lead to mixing of chemical species and contribute to the transport of angular momentum and magnetic fields. We present a series of fully nonlinear, three-dimensional (3D) anelastic simulations of overshooting convection in a spherical shell that are focused on the dependence of the overshooting dynamics on the density stratification and the rotation, both key ingredients in stars that however have not been studied systematically together via global simulations. We demonstrate that the overshoot lengthscale is not simply a monotonic function of the density stratification in the convective region, but instead it depends on the ratio of the density stratifications in the two zones. Additionally, we find that the overshoot lengthscale decreases with decreasing Rossby number Ro and scales as Ro while it also depends on latitude with higher Rossby cases leading to a weaker latitudinal variation. We examine the mean flows arising due to rotation and find that they extend beyond the base of the convection zone into the stable region. Our findings may provide a better understanding of the dynamical interaction between stellar convective and radiative regions, and motivate future studies particularly related to the solar tachocline and the implications of its overlapping with the overshoot region.
对流区域的湍流运动过度延伸到相邻的稳定分层区域在恒星内部动力学中起着重要作用，因为这个过程可能导致化学物质的混合，并有助于角动量和磁场的传输。我们展示了一系列在球壳中进行的关于过冲对流的全非线性、三维（3D）滞弹性模拟，这些模拟聚焦于过冲动力学对密度分层和旋转的依赖性，而密度分层和旋转是恒星中的两个关键因素，但尚未通过全局模拟系统地一起研究过。我们证明，过冲长度尺度并非简单地是对流区域中密度分层的单调函数，而是取决于两个区域中密度分层的比值。此外，我们发现过冲长度尺度随着罗斯比数Ro的减小而减小，并且与Ro成比例，同时它还取决于纬度，罗斯比数较高的情况导致较弱的纬度变化。我们研究了由旋转产生的平均流，发现它们延伸到对流区底部之外进入稳定区域。我们的发现可能有助于更好地理解恒星对流区和辐射区之间的动力学相互作用，并推动未来特别是与太阳 tachocline 及其与过冲区域重叠的影响相关的研究。
