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arXiv 1508.04423astro-ph.SR
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形成IRIS诊断VI。太阳大气中133.5 nm C II谱线的诊断潜能

The formation of IRIS diagnostics VI. The Diagnostic Potential of the C II Lines at 133.5 nm in the Solar Atmosphere

Bhavna Rathore, Mats Carlsson, Jorrit Leenaarts, Bart De Pontieu

摘要:

我们使用3D辐射磁流体动力学模型来研究模拟中的热力学量如何以可观测的量编码,从而探索133.5 nm线的诊断潜力。我们发现线芯强度与地层高度的温度有相关性,但相关性很弱,特别是当线芯强度较强时。线芯多普勒频移是在地层高度处的视线速度的良好量度。线宽取决于吸收曲线的宽度(热和非热宽度)和1.2-4的不透明度增宽因子,这是由于光学粗线形成,对于双峰曲线具有更大的增宽。133.5 nm线可以形成为高于和低于Mg II k线的核心,这取决于在14-50 kK温度范围内的等离子体的量。在该温度范围内更多的等离子体给出相对于Mg II k线芯更高的133.5nm形成高度。合成线的配置文件进行了比较IRIS观测。从模拟的线剖面导出的参数覆盖了观测中看到的参数范围,但平均而言,合成剖面太窄。我们将这种差异解释为在模拟箱中色球温度下缺乏等离子体和太小的非热速度的组合。合成谱和观测谱之间的性质分布的巨大差异表明,133.5 nm谱线是上色球层和下过渡区的强有力的诊断。

英文摘要:

We use 3D radiation magnetohydrodynamic models to investigate how the thermodynamic quantities in the simulation are encoded in observable quantities, thus exploring the diagnostic potential of the 133.5 nm lines. We find that the line core intensity is correlated with the temperature at the formation height but the correlation is rather weak, especially when the lines are strong. The line core Doppler shift is a good measure of the line-of-sight velocity at the formation height. The line width is both dependent on the width of the absorption profile (thermal and non-thermal width) and an opacity broadening factor of 1.2-4 due to the optically thick line formation with a larger broadening for double peak profiles. The 133.5 nm lines can be formed both higher and lower than the core of the Mg II k line depending on the amount of plasma in the 14-50 kK temperature range. More plasma in this temperature range gives a higher 133.5 nm formation height relative to the Mg II k line core. The synthetic line profiles have been compared with IRIS observations. The derived parameters from the simulated line profiles cover the parameter range seen in observations but on average the synthetic profiles are too narrow. We interpret this discrepancy as a combination of a lack of plasma at chromospheric temperatures in the simulation box and too small non-thermal velocities. The large differences in the distribution of properties between the synthetic profiles and the observed ones show that the 133.5 nm lines are powerful diagnostics of the upper chromosphere and lower transition region.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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