Quantifying mixing by shear instabilities in stellar interiors

该程序将数学研究与计算机建模相结合，以更好地了解物质是如何在恒星内部混合的。这些详细的计算模拟结果将转化为一种适合指导天文学界广泛使用的计算机模型的形式，以了解恒星的整个生命周期。该项目将构成博士论文的基础，并为加州大学洛杉矶分校的本科生提供获得有价值的研究培训的机会。在这项努力的同时，PI和她的学生将参加下一届国际天体物理建模研究所，这是一个为期6周的项目，旨在解决天体物理中的热点突出问题。该项目旨在通过密集的研究经验培养特定领域的研究生，并通过学生的共同指导来促进更多资深研究人员之间的长期合作。这一建议是关于在旋转恒星的稳定层状区中获得流体动力剪切不稳定引起的混合(热量、动量、角动量和化学物种)的可靠的定量估计。对于给定的输入强迫、旋转率和给定的流体参数，将运行数值模拟来测量全球结果，例如(1)所产生的平衡切变廓线和层结廓线(2)湍流雷诺应力以及热量和化学物质的湍流通量。结果将用于验证或使现有的混合配方无效，并在必要时创建新的配方。最后，该模型将被实现为恒星演化代码(如MESA)，并应用于最近的恒星地震观测提出的几个选择性动力学问题(特别是红巨星的自转轮廓)。

This program combines mathematical studies with computer modeling to better understand how material gets mixed inside of stars. The results of these detailed computational simulations will be translated into a form suitable to guide computer models that are widely used by the astronomical community to understand the entire life cycle of stars. This program will form the basis of a PhD thesis and provide opportunities for UCSC undergraduates to gain valuable research training. In conjunction with this effort, the PI and her students will be involved with the next International Summer-Institute for Modeling in Astrophysics, a 6-week long program to solve topical outstanding problems in astrophysics. The program aims to train graduate students in a particular field through intense research experience, and to catalyze long-lasting collaborations between more senior researchers through shared mentorship of a student. This proposal is concerned with obtaining robust quantitative estimates for mixing (of heat, momentum, angular momentum and chemical species) induced by hydrodynamic shear instabilities in stably stratified regions of rotating stars. Numerical simulations will be run to measure, for given input forcing, rotation rate, and given fluid parameters, global outcomes such as (1) the resulting shear profile and stratification profile at equilibrium (2) the turbulent Reynolds stresses and turbulent fluxes of heat and chemical species. The results will be used to validate or invalidate existing mixing prescription and to create new prescriptions as necessary. Finally, the model will be implemented into stellar evolution codes (such as MESA), and applied to a few choice dynamical problems (notably, the rotation profiles of red giants) raised by recent asteroseismic observations.