Solar coronal plumes long seemed to possess a simple geometry supporting spatially coherent, stable outflow without significant fine structure. Recent high-resolution observations have challenged this picture by revealing numerous transient, small-scale, collimated outflows ("jetlets") at the base of plumes. The dynamic filamentary structure of solar plumes above these outflows, and its relationship with the overall plume structure, have remained largely unexplored. We analyzed the statistics of continuously observed fine structure inside a single representative bright plume within a mid-latitude coronal hole during 2016 July 2-3. By applying advanced edge-enhancement and spatiotemporal analysis techniques to extended series of high-resolution images from the Solar Dynamics Observatory's Atmospheric Imaging Assembly, we determined that the plume was composed of numerous time-evolving filamentary substructures, referred to as "plumelets" in this paper, that accounted for most of the plume emission. The number of simultaneously identifiable plumelets was positively correlated with plume brightness, peaked in the fully formed plume, and remained saturated thereafter. The plumelets had transverse widths of 10 Mm and intermittently supported upwardly propagating periodic disturbances with phase speeds of 190-260 km/s and longitudinal wavelengths of 55-65 Mm. The characteristic frequency (3.5 mHz) is commensurate with that of solar p-modes. Oscillations in neighboring plumelets are uncorrelated, indicating that the waves could be driven by p-mode flows at spatial scales smaller than the plumelet separation. Multiple independent sources of outflow within a single coronal plume should impart significant fine structure to the solar wind that may be detectable by Parker Solar Probe and Solar Orbiter.

中文翻译：

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羽柱：日冕羽中的动态丝状结构

长期以来，日冕羽流似乎具有简单的几何形状，支持空间连贯、稳定的流出，而没有显着的精细结构。最近的高分辨率观测揭示了羽流底部的大量瞬态、小规模、准直的外流（“喷射流”），从而对这一图片提出了挑战。这些流出物上方的太阳羽流的动态丝状结构及其与整体羽流结构的关系在很大程度上仍未得到探索。我们分析了 2016 年 7 月 2 日至 3 日期间中纬度日冕洞内单个具有代表性的明亮羽流内部连续观测到的精细结构统计数据。通过将先进的边缘增强和时空分析技术应用于来自太阳动力学天文台大气成像组件的高分辨率图像系列，我们确定羽流由许多随时间演变的丝状亚结构组成，在本文中称为“羽流”，占羽流排放的大部分。同时可识别的羽流数量与羽流亮度呈正相关，在完全形成的羽流中达到峰值，此后保持饱和。羽流的横向宽度为 10 毫米，间歇性地支持向上传播的周期性扰动，相位速度为 190-260 公里/秒，纵向波长为 55-65 毫米。特征频率 (3.5 mHz) 与太阳 p 模式的特征频率相称。相邻羽流中的振荡是不相关的，这表明波可能由空间尺度小于羽流间隔的 p 模式流驱动。