High-resolution Observations of Plume Footpoints in a Solar Coronal Hole
High-resolution Observations of Plume Footpoints in a Solar Coronal Hole
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DOI：
10.3847/1538-4357/acd456
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发表时间：
2023-08
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通讯作者：
Kyungsuk Cho;Pankaj Kumar;I. Cho;M. Madjarska;V. Nakariakov;E. Lim;W. Cao;V. Yurchyshyn;Xu Yang;Sung Park
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作者：
Kyungsuk Cho;Pankaj Kumar;I. Cho;M. Madjarska;V. Nakariakov;E. Lim;W. Cao;V. Yurchyshyn;Xu Yang;Sung Park
日珥柱是日冕洞中从太阳表面延伸到日冕的明亮结构，被认为是太阳风的一个可能来源。人们认为日珥柱扎根于强单极光球磁通量斑块（网络/谱斑区域）。日珥柱底部的磁活动可能在产生外流和传播扰动（PDs）方面发挥关键作用。然而，日珥柱底部的光球/色球活动（例如喷流/针状体）的作用及其与传播扰动的联系，人们了解甚少。利用1.6米古德太阳望远镜（GST）、界面区成像光谱仪（IRIS）以及太阳动力学观测台搭载的大气成像组件（AIA）于2020年7月23日对日珥柱进行的高分辨率观测，我们分析了日珥柱底部的色球/过渡区活动及其与日珥柱中外流/传播扰动的联系。GST可见成像光谱仪图像显示，在日珥柱足点处有重复出现且发射谱线蓝移（伪多普勒图）的针状体。此外，光球磁图证明日珥柱底部存在混合极性。IRIS的Mg II k 多普勒图显示，在日珥柱足点处有强烈的蓝移发射（约50千米/秒）和较高的亮温度（Mg II k2 谱线）。沿日珥柱（AIA 171埃）的长周期传播扰动（周期P≈20 - 25分钟）与色球图像中针状体的周期性相符，这表明针状体与传播扰动之间存在紧密联系。我们认为，日珥柱足点处日冕亮点的闭合和开放磁通量之间的互换重联，最有可能是产生沿日珥柱的上升流及相关传播扰动的原因。
Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume’s footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg ii k Dopplergrams show strong blueshifted emission (∼50 km s−1) and a high brightness temperature (Mg ii k2 line) at the footpoint of the plume. The long-period PDs (P ≈ 20–25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume’s footpoint is the most likely candidate to produce upflows and associated PDs along the plume.