Spectral Characteristics of Solar Flares in Different Chromospheric Lines and Their Implications
Spectral Characteristics of Solar Flares in Different Chromospheric Lines and Their Implications
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DOI：
10.1007/s11207-007-0282-y
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发表时间：
2007-05
期刊：
影响因子：
2.8
通讯作者：
Hui Li;J. You;Xing-feng Yu;Q. Du
中科院分区：
文献类型：
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作者：
Hui Li;J. You;Xing-feng Yu;Q. Du
利用紫金山天文台太阳摄谱仪红外探测系统观测到的典型太阳耀斑的光谱数据，研究了耀斑在不同位相和不同位置时Hα、Caii 8 542 π和Hei 10 830 π谱线的光谱特征，并结合空间观测讨论了其可能的意义。结果表明，在耀斑的初始阶段，Hα线只出现红移，没有宽翼。在耀斑爆发后几分钟内，在有和没有非热过程的盘状耀斑和盘缘耀斑中，都观察到Hα线在3 - 5 ″的小区域内的大加宽。类似于阻尼展宽的远翼不仅出现在Hα谱线上，而且在Hei 10 830耀斑谱线上，在非热过程的耀斑中也同样存在。有时，我们甚至在盘状耀斑中的Caii 8 542 Å线中检测到微弱的远翼发射。在足点和耀斑环顶区域都观察到这种大的增宽，可能是强烈湍流和/或宏观运动造成的。因此，所谓的Hα线剖面的非热翼并不是区分耀斑中非热电子是否被加速的充分条件。Caii 8 542日冕谱线在环顶区域显示出较低的强度，而在靠近太阳表面的部分显示出较高的强度。发射大于附近的连续在Hei 10 830线只在小区域检测到强X射线发射和避免太阳黑子本影。
Using the spectral data of representative solar flares observed with the infrared detector system of the solar spectrograph at Purple Mountain Observatory, we study the spectroscopic characteristics of solar flares in the Hα, the Caii8 542 Å, and the Hei10 830 Å lines in different phases and various locations of flares and discuss their possible implications coupled with space observations. Our results show that in the initial phase of a flare the Hα line displays a red shift only with no wide wing. Large broadenings of the Hα line are observed a few minutes after the flare onset within small regions of 3 – 5′′in both disk and limb flares with and without nonthermal processes. Far wings similar to those of damping broadening appear not only in the Hα line but in the Hei10 830 Å line as well in flares with nonthermal processes. Sometimes we even detect weak far-wing emission in the Caii8 542 Å line in disk flares. Such large broadenings are observed in both the footpoints and the flare loop-top regions and possibly result from strong turbulence and/or macroscopic motions. Therefore, the so-called nonthermal wing of the Hα line profile is not a sufficient condition to distinguish whether nonthermal electrons are accelerated or not in a flare. The Caii8 542 Å line shows lower intensity in the loop-top regions and higher intensity in the parts close to the solar surface. Emissions larger than nearby continuum in the Hei10 830 Å line are detected only in small regions with strong X-ray emissions and avoid sunspot umbrae.