Atmosphere and spectrum modelling of cool stars

星星最外层的半透明层构成了星星的大气层，也是我们最能直接观察到的星星的一部分。 我们研究大气层的主要观测数据是星星发出的光谱。 光谱如何由大气结构决定的物理学非常复杂，我们只能通过对大气和光谱的计算建模来提取有关星星的信息。 因此，推断大气结构的准确性取决于计算模型的物理真实性。 由于计算能力和数值方法的限制，迄今为止的模型都是对实际恒星大气的不切实际的近似。 我建议在恒星大气和光谱建模的现实主义的一些领域，包括大气的几何形状和水平结构，气体和辐射场的热力学状态的治疗，包括外流（风），和现实主义的原子吸收，然后重新发射，光子的改进。 这是一个雄心勃勃的计划，但该方法将强调在其中一些领域进行近似改进，同时在其他领域进行更现实的改进，以同时研究几个领域改进的净综合效果。 这些改进尤其适用于研究相对较冷的恒星，如太阳和红巨星。 有两个广泛的科学问题需要解决：1）提高光谱测定我们银河系中追踪遥远的全球结构的非常古老的红巨星的化学成分的准确性，对它的理解将有助于阐明宇宙中结构形成和化学元素合成的历史，2）在太阳和大多数冷恒星的外层大气中发现的神秘的剧烈温度反转的结构，对它的理解将揭示目前未知的恒星大气中发生的物理过程。

The outermost translucent layers of a star comprise the star's atmosphere, and is the part of the star thatwe can observe most directly.  The primary observational data that we have for studying the atmosphere isthe spectrum of the light emitted by the star.  The physics of how the spectrum is determined by thestructure of the atmosphere is sufficiently complex that we can only extract information about the star bycomputational modelling of the atmosphere and the spectrum.  It follows that the accuracy with which theatmospheric structure is inferred depends on the physical realism of the computational modelling.  Due tolimitations in computational power and numerical methodology, models to date have been somewhatunrealistic approximations to actual stellar atmospheres.  I propose to make improvements to a number ofareas of realism in stellar atmosphere and spectrum modelling, including the geometry and horizontalstructure of the atmosphere, the treatment of the thermodynamic state of the gas and radiation field, theinclusion of outflows (winds), and the realism with which atoms absorb, then re-emit, photons.  This is anambitious program, but the approach will emphasize making approximate improvements in some of theseareas while making more realistic improvements in others of them to study the net combined effect ofimprovement in several areas at once.  These improvements are especially relevant to the study ofrelatively cool stars such as the Sun and red giants.  There are two broad scientific problems that will beaddressed: 1) Increasing the accuracy with which the chemical composition is spectroscopically determinedfor very old red giant stars that trace remote global structures in our Galaxy, the understanding of whichwill help elucidate the history of structure formation and chemical element synthesis in the Universe, and2) The structure of the mysterious dramatic temperature inversion that is found in the outer atmosphere ofthe Sun and most cool stars, the understanding of which will reveal physical processes that occur in suchstellar atmospheres that are currently unknown.