A Search for High-Frequency Coronal Brightness Variations in the 21 August 2017 Total Solar Eclipse
A Search for High-Frequency Coronal Brightness Variations in the 21 August 2017 Total Solar Eclipse
复制标题
寻找 2017 年 8 月 21 日日全食的高频日冕亮度变化
DOI：
10.1007/s11207-019-1428-4
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发表时间：
2019
期刊：
影响因子：
2.8
通讯作者：
F. Keenan
中科院分区：
文献类型：
--
作者：
P. Rudawy;K. Radziszewski;A. Berlicki;K. Phillips;D. Jess;P. Keys;F. Keenan
我们报告了 2017 年 8 月 21 日从美国爱达荷州观测到的日全食期间日冕绿线（Fe xiv 530.3 nm）发射的短期强度变化的研究。与之前的实验（1999 年和 2001 年日食）相比，我们的实验使用了更加灵敏的探测系统和更好的空间分辨率，从而可以看到安静日冕环和活动区域环系统的精细细节。引导式 200 毫米孔径施密特-卡塞格伦望远镜与最先进的 CCD 相机一起使用，该相机具有 16 位强度辨别力和视场（0.43∘×0.43∘$0.43^{ \circ } \times 0.43^{\circ }$），涵盖了大约三分之一的可见日冕。相机像素大小为 1.55 角秒，而日食期间的视宁度可以解析 ≈2${\approx}\, 2$ 角秒（距太阳 1450 公里）的特征。在整个过程的 122.9 秒部分中，以 3.49s−1$3.49~\mbox{s}^{-1}$ 的帧速率总共记录了 429 个图像。在分析中，我们特别搜索了短周期强度振荡和行波，因为理论预测短周期的快模磁流体动力（MHD）波可能对安静日冕和活动区加热很重要。首先考虑到各种仪器和光度效应，我们使用小波技术在频率范围 0.5–1.6 Hz$0.5\,\mbox{--}\,1.6\mbox{ Hz}$ 的约 404,000$404\mbox{,}000$ 像素中搜索周期性（周期为 2 秒到 0.6 秒）。我们还沿着大约 65 个日冕结构搜索了行波。然而，我们没有发现任何具有统计学意义的证据。这一负面结果大大改善了我们从之前的分析中获得的限制，并且它表明未来对短周期日冕波的搜索可能会更好地针对多普勒频移和强度振荡。
We report on a search for short-period intensity variations in the green-line (Fe xiv 530.3 nm) emission from the solar corona during the 21 August 2017 total eclipse viewed from Idaho in the United States. Our experiment was performed with a much more sensitive detection system, and with better spatial resolution, than on previous occasions (1999 and 2001 eclipses), allowing fine details of quiet coronal loops and an active-region loop system to be seen. A guided 200-mm-aperture Schmidt–Cassegrain telescope was used with a state-of-the-art CCD camera having 16-bit intensity discrimination and a field-of-view (0.43∘×0.43∘$0.43^{ \circ } \times 0.43^{\circ }$) that encompassed approximately one third of the visible corona. The camera pixel size was 1.55 arcseconds, while the seeing during the eclipse enabled features of ≈2${\approx}\, 2$ arcseconds (1450 km on the Sun) to be resolved. A total of 429 images were recorded during a 122.9 second portion of the totality at a frame rate of 3.49s−1$3.49~\mbox{s}^{-1}$. In the analysis, we searched particularly for short-period intensity oscillations and travelling waves, since theory predicts fast-mode magneto-hydrodynamic (MHD) waves with short periods may be important in quiet coronal and active-region heating. Allowing first for various instrumental and photometric effects, we used a wavelet technique to search for periodicities in some 404,000$404\mbox{,}000$ pixels in the frequency range 0.5–1.6 Hz$0.5\,\mbox{--}\,1.6\mbox{ Hz}$ (periods 2 seconds to 0.6 seconds). We also searched for travelling waves along some 65 coronal structures. However, we found no statistically significant evidence in either. This negative result considerably refines the limit that we obtained from our previous analyses, and it indicates that future searches for short-period coronal waves may be better directed towards Doppler shifts as well as intensity oscillations.
DOI：
10.3847/1538-4357/aa5ff9
发表时间：
2017-03
期刊：
The Astrophysical Journal
影响因子：
--
作者：
D. Pontin;M. Janvier;S. K. Tiwari;K. Galsgaard;A. Winebarger;J. Cirtain
通讯作者：
D. Pontin;M. Janvier;S. K. Tiwari;K. Galsgaard;A. Winebarger;J. Cirtain