A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory
A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory
复制标题
太阳动力学观测站观测的活动区域纳耀斑特性调查
DOI：
10.3847/1538-4357/aa7137
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
J. Klimchuk
中科院分区：
文献类型：
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作者：
N. Viall;J. Klimchuk
在本文中，我们检查了15个不同的活动区（AR）与太阳动力学观测和分析其nanoflare属性。我们最近开发了一种技术，系统地识别和测量等离子体温度动态计算光变曲线之间的时间滞后。时间滞后法测试等离子体是否保持在稳定的温度，或者如果它是动态的，经历加热和冷却循环。我们的技术的一个重要方面是，它分析了观测上不同的日冕环以及它们之间更普遍的漫射发射。我们发现，广泛的冷却之前报道的NOAA AR 11082是所有AR的通用属性。结果与脉冲纳米耀斑加热后缓慢冷却一致。然而，只有偶尔才会从7 MK以上完全冷却到远低于1 MK。更常见的是，等离子体在被另一个纳耀斑重新加热之前冷却到大约1-2 MK。Warren等人首先研究了这15个AR。我们发现，冷却程度与报告的排放测量分布斜率相关性不好。我们还得出结论，他们测量的Fe xviii发射等离子体主要处于冷却状态。这些结果支持这样的想法，即纳米片具有能量和频率的分布，单个通量管上的连续事件之间的平均延迟与等离子体冷却时间尺度相当。
In this paper, we examine 15 different active regions (ARs) observed with the Solar Dynamics Observatory and analyze their nanoflare properties. We have recently developed a technique that systematically identifies and measures plasma temperature dynamics by computing time lags between light curves. The time lag method tests whether the plasma is maintained at a steady temperature, or if it is dynamic, undergoing heating and cooling cycles. An important aspect of our technique is that it analyzes both observationally distinct coronal loops as well as the much more prevalent diffuse emission between them. We find that the widespread cooling reported previously for NOAA AR 11082 is a generic property of all ARs. The results are consistent with impulsive nanoflare heating followed by slower cooling. Only occasionally, however, is there full cooling from above 7 MK to well below 1 MK. More often, the plasma cools to approximately 1–2 MK before being reheated by another nanoflare. These same 15 ARs were first studied by Warren et al. We find that the degree of cooling is not well correlated with the reported slopes of the emission measure distribution. We also conclude that the Fe xviii emitting plasma that they measured is mostly in a state of cooling. These results support the idea that nanoflares have a distribution of energies and frequencies, with the average delay between successive events on an individual flux tube being comparable to the plasma cooling timescale.