Detectability of large-scale flows in global helioseismic data: A numerical experiment
Detectability of large-scale flows in global helioseismic data: A numerical experiment
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全球日震数据中大尺度流的可检测性：数值实验
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
R. Komm
中科院分区：
文献类型：
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作者：
M. Roth;R. Howe;R. Komm
对流运动通过改变太阳p模的频率来影响它们。与由差分旋转引起的频率分裂相比，这只是一个很小的附加效应。随着差分旋转的反演的空间分辨率变得更好，重要的是要知道这些额外的频移如何修改分裂系数以及这两种效应如何被解开。因此，我们进行了数值实验。我们使用准简并微扰理论来创建受微分旋转和大尺度流动影响的p模式的频率。对模拟的频率集进行了分析，并对差分旋转进行了反演。我们使用（l，ν）覆盖范围的变化，多重，和反演结果作为诊断，得出结论的大规模流动的可检测性在全球日震数据。结果是对流区大尺度流动的探测极限为10 ms −1。具有较大振幅的扇形极向流将导致旋转速率的显著失真，而具有较大振幅的带状极向流将导致失真的偶a系数和中断的多重态。在这项研究中，我们使用全球日震学的结果结合准简并扰动理论和数值模拟来寻找对流区中的大尺度、长寿命结构。我们集中在（l，ν）覆盖范围的变化，多重态，反演结果和推导出大尺度结构的速度的可探测性限制。这项研究的动机是双重的。一方面，在过去的几年里，太阳的内部结构已经被越来越精确地确定了。特别是随着高质量日震资料的获得，通过反演振荡资料详细研究了差异旋转的性质及其深度依赖性。由于太阳内部分辨率的提高，有必要了解太阳内部物理过程对太阳振荡的较小影响及其对反演结果的影响。
Convective motions affect the solar p-modes by shifting their frequencies. In comparison to the frequency splitting caused by the differential rotation, this is only a small additional effect. As the spatial resolution of the inversions for the differ- ential rotation becomes better, it is important to know how these additional frequency shifts modify the splitting coefficients and how these two effects might be disentangled. Therefore we carry out a numerical experiment. We use quasi-degenerate pertur- bation theory to create frequencies of p-modes that are affected by differential rotation and by large-scale flows. The simulated frequency sets are analyzed and inverted for differential rotation. We use changes in the (l ,ν ) coverage, the multiplets, and the inversion results as diagnostics to draw conclusions about the detectability of large-scale flows in global helioseismic data. The result is a detectability limit of the order of 10ms −1 for large-scale flows in the convection zone. A sectoral poloidal flow with greater amplitude will lead to a noticeable distortion of the rotation rate, while a zonal poloidal flow with greater amplitude will lead to distorted even-a coefficients and disrupted multiplets. In this study, we search for large-scale, long-lived struc- tures in the convection zone by using global helioseismol- ogy results combined with quasi-degenerate perturbation the- ory and numerical simulations. We concentrate on changes in the (l ,ν ) coverage, the multiplets, and the inversion results and derive detectability limits for the velocity of large-scale structures. The motivation for this study is two-fold. On the one hand, the internal structure of the Sun has been determined with in- creasing accuracy within the last few years. Especially with the availability of high-quality helioseismic data the properties of the differential rotation and its depth dependence have been studied in great detail by inverting oscillation data. Because of the improving resolution of the solar interior, it is necessary to know about smaller effects of physical processes in the sun on the solar oscillations and their influences on the inversion results.