Structure and Evolution of Supergranulation from Local Helioseismology
Structure and Evolution of Supergranulation from Local Helioseismology
复制标题
当地日震学中超粒化的结构和演化
DOI：
10.1007/s11207-008-9206-8
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发表时间：
2008
期刊：
影响因子：
2.8
通讯作者：
T. Duvall
中科院分区：
文献类型：
--
作者：
J. Hirzberger;L. Gizon;S. Solanki;T. Duvall
在太阳表面可以看到超级颗粒，它是一种水平流出的细胞状图案。虽然它没有显示出明显的强度模式，但它间接地表现在例如色球网络中。以前的研究报告的超颗粒化现象的推断的基本参数的显着差异。在这里，我们研究的结构和时间演化的一个大样本的超颗粒，测量使用当地日震和SOHO/MDI数据从2000年在太阳活动最低。当地日震学与f模式提供了地图的水平发散的流速在深度约为1微米。从这些发散图超颗粒细胞被确定通过使用傅立叶分割程序在二维和三维（两个空间维度加时间）。我们分析的地图包含超过105个超颗粒细胞和超过103个寿命历史，这使得具有高度统计意义的详细分析成为可能。超颗粒细胞的平均直径为27.1 μ m。根据测量的寿命分布（三维分割），平均寿命估计为1.6天，大细胞的寿命明显长于小细胞。对和标记相关函数不显示明显的功能，规模大于典型的细胞大小，这表明纯粹随机的细胞位置。超颗粒细胞的时间历史表明，从它们生命的前半段出现和生长到它们生命的后半段衰变，它们经历了一个平稳的演化过程（不像爆炸颗粒，它们在破碎之前达到最大尺寸）。
Supergranulation is visible at the solar surface as a cellular pattern of horizontal outflows. Although it does not show a distinct intensity pattern, it manifests itself indirectly in, for example, the chromospheric network. Previous studies have reported significant differences in the inferred basic parameters of the supergranulation phenomenon. Here we study the structure and temporal evolution of a large sample of supergranules, measured by using local helioseismology and SOHO/MDI data from the year 2000 at solar activity minimum. Local helioseismology with f modes provides maps of the horizontal divergence of the flow velocity at a depth of about 1 Mm. From these divergence maps supergranular cells were identified by using Fourier segmentation procedures in two dimensions and in three dimensions (two spatial dimensions plus time). The maps that we analyzed contain more than 105 supergranular cells and more than 103 lifetime histories, which makes possible a detailed analysis with high statistical significance. We find that the supergranular cells have a mean diameter of 27.1 Mm. The mean lifetime is estimated to be 1.6 days from the measured distribution of lifetimes (three-dimensional segmentation), with a clear tendency for larger cells to live longer than smaller ones. The pair and mark correlation functions do not show pronounced features on scales larger than the typical cell size, which suggests purely random cell positions. The temporal histories of supergranular cells indicate a smooth evolution from their emergence and growth in the first half of their lives to their decay in the second half of their lives (unlike exploding granules, which reach their maximum size just before they fragment).