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Quantifying mixing by shear instabilities in stellar interiors: differential rotation

通过恒星内部的剪切不稳定性来量化混合：微分旋转

基本信息

批准号：
1814327
负责人：
Pascale Garaud
金额：
$ 28.55万
依托单位：
University of California-Santa Cruz
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-09-01 至 2022-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1814327&HistoricalAwards=false
关键词：
Quantifying mixing shear instabilities stellar

项目摘要

Understanding the details of the interiors of stars and of their evolution with time requires a combination of careful observations and sophisticated theoretical models. This research team at the University of California-Santa Cruz will provide improved, numerically-validated quantitative computer models for the transport and mixing of gases and energy within stellar interiors. The research will bring up to date prescriptions derived nearly 30 years ago that have never strictly been tested. The work is of fundamental importance for scientific investigations into the internal rotation of stars. This is particularly relevant today, when stellar interiors are being probed with asteroseismology observations. The principal investigator will continue to advise young researchers at all levels. She is involved at the executive level in two international graduate training programs, the Woods Hole Geophysical Fluid Dynamics (GFD) program, and the Kavli Summer Program in Astrophysics. She helps run the programs and advises students through them. The next GFD program will be focused on topics similar to this research project.The PI and her team will obtain 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 in rotating Cartesian domains located at various latitudes in the star using the shearing-box formalism. The simulations will be used to measure, for given shearing rate, rotation rate, and fluid parameters, global outcomes such as the turbulent Reynolds stresses, turbulent fluxes of heat, and the chemical species. Two regimes will be explored, one in which the effects of thermal diffusion are important (the low Peclet number limit) and one in which they are not. The latter is the standard shear instability problem, while the former has been invoked as an alternative mechanism called secular shear instability. The results will be used to validate or invalidate existing mixing prescriptions, and create new prescriptions as necessary. The team also plans to look at both baroclinically stable and unstable cases.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

要了解恒星内部的细节以及它们随时间的演变，需要结合仔细的观察和复杂的理论模型。加州大学圣克鲁斯分校的这个研究小组将为恒星内部气体和能量的传输和混合提供改进的、经过数值验证的定量计算机模型。这项研究将带来近30年前的最新处方，这些处方从未经过严格测试。这项工作对科学研究恒星的内部旋转具有重要意义。当我们用星震学观测来探测恒星内部时，这一点在今天尤为重要。首席研究员将继续为各级年轻研究人员提供建议。她参与了两个国际研究生培训项目，伍兹霍尔地球物理流体动力学（GFD）项目和Kavli天体物理学暑期项目。她帮助管理这些项目，并通过这些项目为学生提供建议。下一个GFD项目将集中在与本研究项目类似的主题上。PI和她的团队将获得由旋转恒星稳定分层区域的流体动力剪切不稳定性引起的混合（热、动量、角动量和化学物质）的可靠定量估计。数值模拟将在位于恒星不同纬度的旋转笛卡尔域中使用剪切盒形式进行。对于给定的剪切速率、旋转速率和流体参数，模拟将用于测量诸如湍流雷诺应力、湍流热通量和化学物质等全局结果。我们将探讨两种情况，其中一种情况下热扩散的影响是重要的（低佩莱特数限制），另一种情况下则不是。后者是标准的剪切失稳问题，而前者被称为长期剪切失稳的替代机制。结果将用于验证或取消现有的混合处方，并根据需要创建新的处方。该团队还计划研究临床压力稳定和不稳定的病例。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。