OPTICAL SPECTRAL OBSERVATIONS OF A FLICKERING WHITE-LIGHT KERNEL IN A C1 SOLAR FLARE
OPTICAL SPECTRAL OBSERVATIONS OF A FLICKERING WHITE-LIGHT KERNEL IN A C1 SOLAR FLARE
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DOI：
10.1088/0004-637x/798/2/107
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发表时间：
2014-11
期刊：
影响因子：
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通讯作者：
A. Kowalski;G. Cauzzi;L. Fletcher
中科院分区：
文献类型：
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作者：
A. Kowalski;G. Cauzzi;L. Fletcher
我们分析了2011年8月18日发生在AR 11271 （sol2011-08-18:15）内的一个双带长持续C1.1耀斑的光谱。耀斑的脉冲阶段是用一套全面的星载和地面仪器观测到的，这些仪器提供了一系列独特的低层耀斑大气诊断。在这里，我们报告了在邓恩太阳望远镜的水平摄谱仪获得的3600 Å至4550 Å的低分辨率光谱中观测到的增强连续光谱发射的检测。一个小的，< 0。″5 （1015 cm2）半影/本影核在光学连续体和色球发射线中反复变亮，与费米航天器上的伽马射线暴监测仪检测到的硬x射线变化的时间特征相似。辐射流体动力学耀斑模型采用的非热电子束能量通量高到足以在我们的耀斑光谱中产生光学对比，该模型预测发射中会出现较大的巴尔默跳变，表明来自耀斑上部色球层的氢复合辐射。然而，我们在连续体过剩的最蓝光谱区域没有发现这样一个巴尔默跳变的证据。就在预期的巴尔默跃迁之后，我们发现了过量辐射中“蓝色连续体碰撞”的证据，这可能表明了高阶巴尔默线的合并。大量的观测约束条件为用辐射流体动力学代码模拟这一特殊耀斑的蓝色/光学发射提供了一个跳板，这对于理解这些波长的连续体和发射线辐射的不透明度效应是必要的。
We analyze optical spectra of a two-ribbon, long-duration C1.1 flare that occurred on 2011 August 18 within AR 11271 (SOL2011-08-18T15:15). The impulsive phase of the flare was observed with a comprehensive set of space-borne and ground-based instruments, which provide a range of unique diagnostics of the lower flaring atmosphere. Here we report the detection of enhanced continuum emission, observed in low-resolution spectra from 3600 Å to 4550 Å acquired with the Horizontal Spectrograph at the Dunn Solar Telescope. A small, ⩽0.″5 (1015 cm2) penumbral/umbral kernel brightens repeatedly in the optical continuum and chromospheric emission lines, similar to the temporal characteristics of the hard X-ray variation as detected by the Gamma-ray Burst Monitor on the Fermi spacecraft. Radiative-hydrodynamic flare models that employ a nonthermal electron beam energy flux high enough to produce the optical contrast in our flare spectra would predict a large Balmer jump in emission, indicative of hydrogen recombination radiation from the upper flare chromosphere. However, we find no evidence of such a Balmer jump in the bluemost spectral region of the continuum excess. Just redward of the expected Balmer jump, we find evidence of a “blue continuum bump” in the excess emission which may be indicative of the merging of the higher order Balmer lines. The large number of observational constraints provides a springboard for modeling the blue/optical emission for this particular flare with radiative-hydrodynamic codes, which are necessary to understand the opacity effects for the continuum and emission line radiation at these wavelengths.