Modeling of the Hydrogen Lyman Lines in Solar Flares
Modeling of the Hydrogen Lyman Lines in Solar Flares
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DOI：
10.3847/1538-4357/aacc29
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发表时间：
2018-07
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影响因子：
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通讯作者：
Stephen Brown;L. Fletcher;G. Kerr;N. Labrosse;A. Kowalski;Jaime de la Cruz Rodr'iguez
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文献类型：
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作者：
Stephen Brown;L. Fletcher;G. Kerr;N. Labrosse;A. Kowalski;Jaime de la Cruz Rodr'iguez
氢的莱曼线(91.2nmlt；λ<；121.6 nm)对太阳色球的辐射损失有重要贡献，并且在耀斑过程中增强。我们以前已经证明，太阳动力学观测站上的极端紫外线变率仪器观测到的莱曼线呈现出相当于30公里S−1量级速度的多普勒运动。然而，与预期相反的是，红移和蓝移都存在，没有观察到主要的流动方向。为了了解莱曼线的形成，特别是它们的多普勒运动，我们用辐射流体动力学程序RADYN和辐射传输程序RH模拟了耀斑色球的演化和太阳耀斑期间莱曼线的响应。我们发现，模拟大气中的上行气流导致了线芯的蓝移，呈现出中心反转。然后，我们使用极端紫外线变异性实验(EVE)仪器的属性来模拟仪器对剖面的影响。在它们与仪器测线剖面卷积后，可能被解释为谱线中的下行(红移发射)，不一定对应于实际的下行。大气中的动态特征可以在谱线轮廓中引入复杂的特征，这些特征不会被光谱分辨率为EVE的仪器探测到，但在太阳轨道器上的日冕环境光谱调查仪器的分辨率上留下了更多的特征。
The hydrogen Lyman lines (91.2 nm < λ < 121.6 nm) are significant contributors to the radiative losses of the solar chromosphere, and they are enhanced during flares. We have shown previously that the Lyman lines observed by the Extreme Ultraviolet Variability instrument onboard the Solar Dynamics Observatory exhibit Doppler motions equivalent to speeds on the order of 30 km s−1. However, contrary to expectations, both redshifts and blueshifts were present and no dominant flow direction was observed. To understand the formation of the Lyman lines, particularly their Doppler motions, we have used the radiative hydrodynamic code, RADYN, along with the radiative transfer code, RH, to simulate the evolution of the flaring chromosphere and the response of the Lyman lines during solar flares. We find that upflows in the simulated atmospheres lead to blueshifts in the line cores, which exhibit central reversals. We then model the effects of the instrument on the profiles, using the Extreme Ultraviolet Variability Experiment (EVE) instrument's properties. What may be interpreted as downflows (redshifted emission) in the lines, after they have been convolved with the instrumental line profile, may not necessarily correspond to actual downflows. Dynamic features in the atmosphere can introduce complex features in the line profiles that will not be detected by instruments with the spectral resolution of EVE, but which leave more of a signature at the resolution of the Spectral Investigation of the Coronal Environment instrument onboard the Solar Orbiter.