恒星大气外层辐射等离子体的降阶NLTE动力学模型
A reduced-order NLTE kinetic model for radiating plasmas of outer envelopes of stellar atmospheres
摘要：
目前的工作提出了一个自洽的降阶NLTE动力学模型辐射等离子体，如发现在恒星大气的外层。从最新的从头算和实验数据，高度复杂的碰撞-辐射动力学机制，简化了集中的束缚能状态的群体。不同的分组策略进行了研究，如均匀和麦克斯韦-玻尔兹曼。基于矩量法得到了材料气体和辐射场的简化控制方程组。应用考虑了部分电离氢中激波的定常流动。结果表明，采用麦克斯韦-玻尔兹曼分组允许，一方面，大量减少未知数的数量，另一方面，以保持气体和辐射量的准确性。据观察，当忽略线辐射时，使用两个组已经导致光电离前体、内部弛豫和辐射冷却区域的非常精确的分辨率。线辐射的包含需要采用仅仅一个额外的组来解释巴尔末和帕邢系的α、β和γ线中的光学薄损耗。在很宽的冲击波速度范围内观察到这种趋势。
英文摘要：
The present work proposes a self-consistent reduced-order NLTE kinetic model for radiating plasmas such as are found in the outer layers of stellar atmospheres. Starting from the most up-to-date set of ab-initio and experimental data, the highly complex collisional-radiative kinetic mechanism is simplified by lumping the bound energy states in groups. Different grouping strategies are investigated, such as uniform and Maxwell-Boltzmann. The reduced set of governing equations for the material gas and the radiation field is obtained based on a moment method. Applications consider the steady flow across a shock wave in partially ionized hydrogen. The results show that adopting a Maxwell-Boltzmann grouping allows, on the one hand, for a substantial reduction of the number of unknowns and, on the other, to maintain accuracy for both gas and radiation quantities. It is observed that, when neglecting line radiation, the use of two groups already leads to a very accurate resolution of the photo-ionization precursor, internal relaxation and radiative cooling regions. The inclusion of line radiation requires adopting just one additional group to account for optically thin losses in the alpha, beta and gamma lines of the Balmer and Paschen series. This trend has been observed for a wide range of shock wave velocities.
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