The Fine-scale Structure of Polar Coronal Holes
The Fine-scale Structure of Polar Coronal Holes
复制标题
DOI：
10.3847/1538-4357/acea7c
复制
发表时间：
2023-08
期刊：
影响因子：
--
通讯作者：
R. Morton;R. Cunningham
中科院分区：
文献类型：
--
作者：
R. Morton;R. Cunningham
日冕洞被认为是由相对较宽的柱状结构组成的，称为羽状物。在这里，我们证明了极冕洞中的羽流(和羽间羽流)是由细小的丝状结构组成的，平均尺度为2“-10”。这种精细的结构是Uritsky等人之前发现的“羽毛”的非肢体类似物。临时性观测使得能够在不受视线上的底层大气影响的情况下对精细结构进行检查。因此，我们认为这种细尺度结构至少在太阳动力学观测站的视场边缘存在。精细结构的空间分布符合k-−-1幂定律，垂直于推断的磁场方向。对于细微结构的小样本，测量作为高度函数的横截面轮廓。在某些情况下，测量表明，精细结构以超辐射方式扩展，这与现有的极场扩展和羽流扩展模型一致。我们讨论了精细结构的存在对于理解日冕洞中的波传播以及它们对太阳风提供能量的贡献的意义。
Coronal holes are thought to be composed of relatively broad columnar structures known as plumes. Here, we demonstrate that the plumes (and interplumes) in polar coronal holes are composed of fine-scale filamentary structure, with average scales of 2″–10″. The fine structure is the off-limb analog of the previously found “plumelets” of Uritsky et al. The off-limb observations enable an examination of the fine structure without the influence of the underlying atmosphere along the line of sight. Hence, we show that the fine-scale structure is present at least until the edge of the field of view of the Solar Dynamics Observatory. The fine structure is found to have spatial distribution that follows a k −1 power law perpendicular to the inferred magnetic field direction. For a small sample of the fine structure, the cross-sectional profiles are measured as a function of height. In some cases, the measurements indicate that the fine structure expands super-radially, consistent with existing models of polar field expansion and the expansion of the plumes. We discuss the implications of the presence of the fine structure with respect to understanding wave propagation in the coronal holes and their contribution to powering the solar wind.