Evolving Active Region Loops Observed with the Transition Region and Coronal Explorer. I. Observations
Evolving Active Region Loops Observed with the Transition Region and Coronal Explorer. I. Observations
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使用过渡区域和日冕探测器观察到的不断变化的活动区域环。
DOI：
10.1086/376679
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
D. Seaton
中科院分区：
文献类型：
--
作者：
A. Winebarger;H. Warren;D. Seaton
使用TRACE进行的观察检测到了一类持续活动区域环路，它们具有固定的195/171？滤波比。这些环的强度意味着比流体动力学方程的静态解的密度大3个数量级的密度。最近有人提出，这些环是一束束脉冲加热的线束，正在通过痕迹通带冷却。这种情况意味着，在出现在较冷的(Fe IX/X 171？)轨迹过滤器图像之前，回路将出现在较热的(Fe XV 284？或Fe XII 195？)轨迹过滤器图像中。在本文中，我们通过检测多迹极紫外滤波图像中五个活动区域环路的时间演化来检验这一假设。我们发现，所有的环路都出现在较热的滤镜图像中，然后才出现在较冷的滤镜图像中。然后，我们使用测量的延迟来估计冷却时间，并发现五个回路中有四个的寿命大于冷却回路的预期寿命。这些结果与这样的假设是一致的，即每个表观环路都是一束顺序加热的线束；其他解释也将被讨论。为了便于在这些环路和流体力学模拟之间进行比较，我们使用了一种新的技术来估计环路长度和几何形状。
Observations made with TRACE have detected a class of persistent active region loops that have flat 195/171 Å filter ratios. The intensity of these loops implies a density that is as much as 3 orders of magnitude larger than the densities of static solutions to the hydrodynamic equations. It has recently been suggested that these loops are bundles of impulsively heated strands that are cooling through the TRACE passbands. This scenario implies that the loops would appear in the hotter (Fe XV 284 Å or Fe XII 195 Å) TRACE filter images before appearing in the cooler (Fe IX/X 171 Å) TRACE filter images. In this paper, we test this hypothesis by examining the temporal evolution of five active region loops in multiple TRACE EUV filter images. We find that all the loops appear in the hotter filter images before appearing in cooler filter images. We then use the measured delay to estimate a cooling time and find that four of the five loops have lifetimes greater than the expected lifetime of a cooling loop. These results are consistent with the hypothesis that each apparent loop is a bundle of sequentially heated strands; other explanations will also be discussed. To facilitate comparisons between these loops and hydrodynamic simulations, we use a new technique to estimate the loop length and geometry.