arXiv 1012.18482010-12astro-ph.SR

恒星中的湍流细胞：I.动能和光度的涨落

Turbulent Cells in Stars: I. Fluctuations in Kinetic Energy and Luminosity

W. David Arnett, Casey Meakin

备注：: 30 pages, 13 figures
DOI：: 10.1088/0004-637X/741/1/33

摘要：

壳体氧燃烧的三维（3D）流体动力学模拟（Meakin和Arnett，2007 b）显示出湍流动能的突发性、周期性波动。这些被证明是由于对流单体的一般不稳定性，只需要一个局部的加热或冷却源。在用混合长度理论（MLT）模拟恒星演化时，这种涨落被抑制了。洛伦兹（Lorenz，1963）的对流卷（胞）模型中也有类似的行为，我们知道它有一个奇异吸引子，会引起速度和光度的混沌涨落。模拟研究表明，洛伦兹对流卷的行为可能类似于对流中的细胞。我们研究了这种最简单近似的一些含义，并提出了改进的途径。使用洛伦兹模型作为对流单体的代表，对流层的多单体模型给出了总光度波动，这暗示了不规则变量（红巨星和超巨星（Schwarzschild 1975）），以及半规则AGB变量中的长次级周期特征（Stothers 2010，Wood，Olivier和Kawaler 2004）。这种“τ机制”是恒星变化的一个新来源，它本质上是非线性的（在线性稳定性分析中看不到），并且与湍流中的不稳定性密切相关。Woodward、Porter和Jacobs（2003年）的3D全球模拟中已经隐含了这一点。这种波动行为在CNeOSi燃烧壳的扩展2D模拟中可以看到（Arnett和Meakin 2011 b），并且可能导致不稳定性，导致核心坍缩超新星的祖先在坍缩之前爆发。

英文摘要：

Three-dimensional (3D) hydrodynamic simulations of shell oxygen burning (Meakin and Arnett, 2007b) exhibit bursty, recurrent fluctuations in turbulent kinetic energy. These are shown to be due to a general instability of the convective cell, requiring only a localized source of heating or cooling. Such fluctuations are shown to be suppressed in simulations of stellar evolution which use mixing-length theory (MLT). Quantitatively similar behavior occurs in the model of a convective roll (cell) of Lorenz (1963), which is known to have a strange attractor that gives rise to chaotic fluctuations in time of velocity and, as we show, luminosity. Study of simulations suggests that the behavior of a Lorenz convective roll may resemble that of a cell in convective flow. We examine some implications of this simplest approximation, and suggest paths for improvement. Using the Lorenz model as representative of a convective cell, a multiple-cell model of a convective layer gives total luminosity fluctuations which are suggestive of irregular variables (red giants and supergiants (Schwarzschild 1975)), and of the long secondary period feature in semi-regular AGB variables (Stothers 2010, Wood, Olivier and Kawaler 2004). This "tau-mechanism" is a new source for stellar variability, which is inherently non-linear (unseen in linear stability analysis), and one closely related to intermittency in turbulence. It was already implicit in the 3D global simulations of Woodward, Porter and Jacobs (2003). This fluctuating behavior is seen in extended 2D simulations of CNeOSi burning shells (Arnett and Meakin 2011b), and may cause instability which leads to eruptions in progenitors of core collapse supernovae PRIOR to collapse.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文