太阳对流区湍流涡度时间相关
Turbulent eddy-time-correlation in the solar convective zone
摘要：
类太阳振荡驱动过程的理论模拟是理解太阳型恒星对流区性质的一个有力途径。在这个框架中，湍流涡旋之间的时间相关性的描述是模式振幅的一个重要组成部分。然而，在涡旋时间关联函数的高斯或洛伦兹描述之间存在争论（Samadi et al. 2003，Chaplin et al. 2005）。事实上，高斯描述再现了太阳模式振幅的低频形状，但从理论角度来看并不令人满意（Houdek，2009），并导致与观测结果的其他分歧（Samadi等人，2007年）。这些都是通过使用洛伦兹描述解决的，但是太阳观测的低频形状没有正确地再现。我们调和这两种描述，通过采用扫描近似，其中包括在假设的涡时间关联函数是由平流的涡，在惯性范围内，由能量轴承涡为主。使用洛伦兹函数以及从扫描假设导出的截止频率，使我们能够再现观测的低频形状。这一结果也证实了太阳情况下高度湍流的扫掠假设。
英文摘要：
Theoretical modeling of the driving processes of solar-like oscillations is a powerful way of understanding the properties of the convective zones of solar-type stars. In this framework, the description of the temporal correlation between turbulent eddies is an essential ingredient to model mode amplitudes. However, there is a debate between a Gaussian or Lorentzian description of the eddy-time correlation function (Samadi et al. 2003, Chaplin et al. 2005). Indeed, a Gaussian description reproduces the low-frequency shape of the mode amplitude for the Sun, but is unsatisfactory from a theoretical point of view (Houdek, 2009) and leads to other disagreements with observations (Samadi et al., 2007). These are solved by using a Lorentzian description, but there the low-frequency shape of the solar observations is not correctly reproduced. We reconcile the two descriptions by adopting the sweeping approximation, which consists in assuming that the eddy-time-correlation function is dominated by the advection of eddies, in the inertial range, by energy-bearing eddies. Using a Lorentzian function together with a cut-off frequency derived from the sweeping assumption allows us to reproduce the low-frequency shape of the observations. This result also constitutes a validation of the sweeping assumption for highly turbulent flows as in the solar case.
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