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arXiv 1507.07594astro-ph.SR
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界面区成像光谱仪观测到的冷过渡区环

Cool transition region loops observed by the Interface Region Imaging Spectrograph

Zhenghua Huang, Lidong Xia, Bo Li, Maria S. Madjarska

摘要:

我们报告了第一台界面区成像光谱仪(IRIS)对冷过渡区环的研究。这类循环在文献中很少受到关注。在活动区NOAA 11934的太阳盘面上,在Si IV 1402.8的光谱光栅和1400的狭缝颚(SJ)图像中观察到了一组这样的环。我们将循环分为三组,并研究它们的动力学和相互作用。第一组由相对稳定的环组成,横截面为382- 626 km。观测到的多普勒速度表明虹吸流,从一端的-10 km/s逐渐变化到另一端的20 km/s。测定了15至25 km/s的非热速度。这些物理性质表明,这些环是由磁重联发生在蓝移的足迹,磁抵消率为$10^{15}$ Mx/s的冲动加热。释放的磁能被重新分配的虹吸流。第二组对应于两个立足点植根于混合磁极性的地区,磁抵消发生在$10^{15}$ Mx/s的速率和线剖面增强翼高达200公里/秒进行了观察。这些都暗示着类似爆炸的事件。结合SJ图像的多普勒速度表明,可能的反平行流在更细的环股。在第三组中,观察到两个冷却回路系统之间的相互作用。两个环系统之间的磁重联的证据反映在爆炸事件的线轮廓,和磁抵消率$3\times10^{15}$ Mx/s在相应的地区观察。IRIS的观测为深入研究冷过渡区环打开了一扇新的机会之窗。进一步的数值实验对于理解它们的物理性质及其在日冕加热过程中的作用至关重要。

英文摘要:

We report on the first Interface Region Imaging Spectrograph (IRIS) study of cool transition region loops. This class of loops has received little attention in the literature. A cluster of such loops was observed on the solar disk in active region NOAA11934, in the Si IV 1402.8 Å spectral raster and 1400 Å slit-jaw (SJ) images. We divide the loops into three groups and study their dynamics and interaction. The first group comprises relatively stable loops, with 382--626\,km cross-sections. Observed Doppler velocities are suggestive of siphon flows, gradually changing from -10 km/s at one end to 20 km/s at the other end of the loops. Nonthermal velocities from 15 to 25 km/s were determined. These physical properties suggest that these loops are impulsively heated by magnetic reconnection occurring at the blue-shifted footpoints where magnetic cancellation with a rate of $10^{15}$ Mx/s is found. The released magnetic energy is redistributed by the siphon flows. The second group corresponds to two footpoints rooted in mixed-magnetic-polarity regions, where magnetic cancellation occurred at a rate of $10^{15}$ Mx/s and line profiles with enhanced wings of up to 200 km/s were observed. These are suggestive of explosive-like events. The Doppler velocities combined with the SJ images suggest possible anti-parallel flows in finer loop strands. In the third group, interaction between two cool loop systems is observed. Evidence for magnetic reconnection between the two loop systems is reflected in the line profiles of explosive events, and a magnetic cancellation rate of $3\times10^{15}$ Mx/s observed in the corresponding area. The IRIS observations have thus opened a new window of opportunity for in-depth investigations of cool transition region loops. Further numerical experiments are crucial for understanding their physics and their role in the coronal heating processes.

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