arXiv 2006.102182020-06-18astro-ph.SR

太阳耀斑早期He I 10830吸收增强的观测和模拟比较

Comparison of Enhanced Absorption in He I 10830 Å in Observations and Modeling During the Early Phase of a Solar Flare

Nengyi Huang, Viacheslav M. Sadykov, Yan Xu, Ju Jing, Haimin Wang

DOI：: 10.3847/2041-8213/ab9b7a

摘要：

He I 10830的三重态是色球活动的一个非常有用的指标，因为氦是太阳大气中第二丰富的元素。利用大熊太阳天文台（BBSO）1.6米古德太阳望远镜（GST）的高分辨率，以前的观测已经显示出两个M级耀斑的增强吸收而不是典型观测到的发射的明确证据。在这项研究中，我们分析了He I 10830 10830的发射在数值模式中的演变，并将其与观测结果进行比较。该模型表示从F-CHROMA数据库中获得的RADYN模拟结果。我们详细考虑了注入电子谱参数接近2013年8月17日耀斑事件观测估计值（$δ=8$，$E_c = \{15,20\}$ keV，$F=\{1\times 10^{11}, 3\times{}10^{11}\}$ erg cm $^{-2}$）的模型，以及其他可用的模型。模拟结果与观测结果吻合得很好，在最大强度降低（-17.1%，与观测值-13.7%相比）和时间变化趋势（初始吸收阶段之后是发射）的意义上。所有模型都显示出He I 10830 10830跃迁初始阶段数密度增加，上下能级粒子数比减小，从而增强了不透明度，形成吸收特征。模型表明，在1.3-1.5 μ m高度处的温度和自由电子密度应该大于$\sim 10^4$ K和$6\times 10^{11}$ cm $^{-3}$阈值，以使谱线开始发射。

英文摘要：

The He I 10830 Å triplet is a very informative indicator of chromospheric activities as the helium is the second most abundant element in the solar atmosphere. Taking advantage of the high resolution of the 1.6 m Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO), previous observations have shown clear evidence of the enhanced absorption, instead of typically-observed emission, for two M-class flares. In this study, we analyze the evolution of the He I 10830 10830 Å emission in numerical models and compare it with observations. The models represent the RADYN simulation results obtained from the F-CHROMA database. We consider the models with the injected electron spectra parameters close to observational estimates for the 2013-August-17 flare event ($δ=8$, $E_c = \{15,20\}$ keV, $F=\{1\times 10^{11}, 3\times{}10^{11}\}$ erg cm$^{-2}$) in detail, as well as other available models. The modeling results agree well with observations, in the sense of both the maximum intensity decrease (-17.1%, compared to the observed value of -13.7%) and the trend of temporal variation (initial absorption phase followed by the emission). All models demonstrate the increased number densities and decreased ratio of the upper and lower level populations of He I 10830 10830 Å transition in the initial phase, which enhances the opacity and forms an absorption feature. Models suggest that the temperatures and free electron densities at heights of 1.3-1.5 Mm should be larger than $\sim 10^4$ K and $6\times 10^{11}$ cm$^{-3}$ thresholds for the line to start being in emission.

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