用COSI程序模拟NLTE太阳辐照度
NLTE solar irradiance modeling with the COSI code
摘要：
上下文已知太阳辐照度在几分钟到几十年的时间尺度上变化，人们怀疑其大幅波动是气候变化的部分原因。目标。我们正在开发一个太阳大气代码，允许物理建模的整个太阳光谱组成的安静的太阳和活跃的地区。这个代码是一个工具，用于模拟太阳辐照度的变化，并了解其对地球的影响。方法.我们利用进一步发展的辐射转移代码COSI，现在纳入分子线的计算。我们验证了COSI条件下的局部热力学平衡（LTE）对合成光谱计算与ATLAS代码。合成的太阳光谱也计算在非本地热力学平衡（NLTE）和可用的测量光谱进行比较。在这样做的时候，我们已经定义了建模的主要问题，例如，缺乏不透明度的紫外光谱的一部分和不一致的计算中的可见光连续水平，我们描述了解决这些问题。结果COSI的改进版本使我们能够达到很好的协议之间的计算和观测到的太阳光谱测量SOLSTICE和SIM板上的SORCE卫星和ATLAS 3任务从航天飞机上运行。我们发现，NLTE效应是非常重要的太阳光谱的建模，即使在光谱的视觉部分，并在整个太阳光谱的变化。除了对光谱的UV部分的强烈影响之外，NLTE效应还影响氢负离子的浓度，这导致可见光连续谱水平和辐照度可变性的显著变化。
英文摘要：
Context. The solar irradiance is known to change on time scales of minutes to decades, and it is suspected that its substantial fluctua- tions are partially responsible for climate variations. Aims. We are developing a solar atmosphere code that allows the physical modeling of the entire solar spectrum composed of quiet Sun and active regions. This code is a tool for modeling the variability of the solar irradiance and understanding its influence on Earth. Methods. We exploit further development of the radiative transfer code COSI that now incorporates the calculation of molecular lines. We validated COSI under the conditions of local thermodynamic equilibrium (LTE) against the synthetic spectra calculated with the ATLAS code. The synthetic solar spectra were also calculated in non-local thermodynamic equilibrium (NLTE) and compared to the available measured spectra. In doing so we have defined the main problems of the modeling, e.g., the lack of opacity in the UV part of the spectrum and the inconsistency in the calculations of the visible continuum level, and we describe a solution to these problems. Results. The improved version of COSI allows us to reach good agreement between the calculated and observed solar spectra as measured by SOLSTICE and SIM onboard the SORCE satellite and ATLAS 3 mission operated from the Space Shuttle. We find that NLTE effects are very important for the modeling of the solar spectrum even in the visual part of the spectrum and for its variability over the entire solar spectrum. In addition to the strong effect on the UV part of the spectrum, NLTE effects influence the concentration of the negative ion of hydrogen, which results in a significant change of the visible continuum level and the irradiance variability.
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