The multi-thermal emission in solar active regions
The multi-thermal emission in solar active regions
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DOI：
10.1051/0004-6361/201321653
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发表时间：
2013-10-01
影响因子：
6.5
通讯作者：
Del Zanna, G.
中科院分区：
文献类型：
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作者：
Del Zanna, G.
我们提出了同时SDO AIA和Hinode EIS的活动区（AR）的热核观测，并评估AIA EUV波段的主要贡献。这是我们以前工作的延伸。我们发现SDO AIA，EVE和EIS观测之间有很好的一致性，使用我们新的EIS校准和最新的EVE v.3数据。我们发现，除了171和335埃，所有的AIA波段都是多热的，并提供了直接从AIA数据粗略估计主要贡献的方法。我们提出并讨论了新的原子数据的AIA波段，表明他们现在已经足够完整，以获得温度信息的核心AR，211埃波段除外。我们发现，新确定的Fe xiv 93.61埃线是占主导地位的贡献94埃带，每当Fe xviii不存在。三种方法来估计在这个波段的Fe xviii发射，两个使用EIS和一个直接从AIA数据。Fe xviii发射通常存在于AR的核心中，但我们发现它在3 MK而不是7 MK形成的情况，这是平衡时峰值离子丰度的温度。讨论了用于元素丰度测定和差分发射测量（DEM）分析的最佳EIS谱线。通过对热3MK环的EIS观测，获得了一组新的元素丰度。低的第一电离电位（FIP）的元素的丰度，相对于那些高FIP元素，被发现被增强约三倍，相比的光球值。路径长度的测量意味着低FIP元素的绝对丰度比光球值高至少三倍。我们提出了一种新的DEM方法定制的AIA波段，研究在1分辨率的AR的热结构。这在一些AR上进行了测试，包括在Hi-C火箭飞行期间观察到的一个AR。我们发现预测和观察到的AIA计数率和EIS辐射之间的良好协议。总的来说，我们发现AIA和Hi-C 193埃日冕结构图像之间的差异很小，尽管Hi-C分辨率更高（0.25）。Hi-C图像和AIA DEM模型表明，AIA已经分辨出一些较冷的环路（低于1兆千瓦），而即使在Hi-C分辨率下，大多数地方仍然无法分辨较热的（1.5 - 2.5兆千瓦）"背景"排放。这种未分辨的发射明显低于以前用TRACE、SOHO CDS和Hinode EIS光谱仪观察到的发射。其增强似乎主要是由于铁丰度增加。我们发现一个无处不在的存在下，在不同的温度下，是不是共空间的发射，并建议未来的高分辨率成像进行等温带。
We present simultaneous SDO AIA and Hinode EIS observations of the hot cores of active regions (ARs) and assess the dominant contributions to the AIA EUV bands. This is an extension of our previous work. We find good agreement between SDO AIA, EVE and EIS observations, using our new EIS calibration and the latest EVE v. 3 data. We find that all the AIA bands are multi-thermal, with the exception of the 171 and 335 angstrom, and provide ways to roughly estimate the main contributions directly from the AIA data. We present and discuss new atomic data for the AIA bands, showing that they are now sufficiently complete to obtain temperature information in the cores of ARs, with the exception of the 211 angstrom band. We found that the newly identified Fe xiv 93.61 angstrom line is the dominant contribution to the 94 angstrom band, whenever Fe xviii is not present. Three methods to estimate the Fe xviii emission in this band are presented, two using EIS and one directly from the AIA data. Fe xviii emission is often present in the cores of ARs, but we found cases where it is formed at 3 MK and not 7 MK, the temperature of peak ion abundance in equilibrium. The best EIS lines for elemental abundance determination and differential emission measure (DEM) analysis are discussed. A new set of abundances for many elements are obtained from EIS observations of hot 3 MK loops. The abundances of the elements with low first ionisation potential (FIP), relative to those of the high-FIP elements, are found to be enhanced by about a factor of three, compared to the photospheric values. A measurement of the path length implies that the absolute abundances of the low-FIP elements are higher than the photospheric values by at least a factor of three. We present a new DEM method customised for the AIA bands, to study the thermal structure of ARs at 1 resolution. This was tested on a few ARs, including one observed during the Hi-C rocket flight. We found excellent agreement between predicted and observed AIA count rates and EIS radiances. Overall we found few differences between the AIA and Hi-C 193 angstrom images of coronal structures, despite the higher Hi-C resolution (0.25). The Hi-C images and the AIA DEM modelling suggest that some of the cooler loops (below 1 MK) are already resolved by AIA, while the hotter (1.5-2.5 MK) " background" emission is in most places still unresolved even at the Hi-C resolution. This unresolved emission is significantly lower than previously observed with TRACE, the SOHO CDS, and Hinode EIS spectrometers. Its enhancement appears to be mostly due to increased iron abundance. We find an ubiquitous presence of emission at different temperatures that is not co-spatial, and suggest that future high-resolution imaging is carried out with isothermal bands.