半矢量：理论
Semiconvection: theory
摘要：
在天体物理条件下（粘度和溶质扩散率低的热扩散率相比）的双扩散层系统中的热量和溶质的传输模型的开发。地层的形成过程不是模型的一部分，但正如在地球物理和实验室环境中观察到的那样，与反射带的寿命相比，假设是快速的。层的厚度是模型的\tbf{a}自由参数。当恒星的能流一定时，有效的双折射扩散系数仅弱依赖于该参数。本文给出了一个在对流区中层厚随时间的演化估计。该模型预测，密度比有一个最大值，一个固定的层状状态可以存在，$R_ρ\la \mr{Le}^{-1/2}$。比较模型预测与网格的数值模拟中提出的配套文件。
英文摘要：
A model is developed for the transport of heat and solute in a system of double-diffusive layers under astrophysical conditions (viscosity and solute diffusivity low compared with the thermal diffusivity). The process of formation of the layers is not part of the model but, as observed in geophysical and laboratory settings, is assumed to be fast compared to the life time of the semiconvective zone. The thickness of the layers is \tbf{a} free parameter of the model. When the energy flux of the star is specified, the effective semiconvective diffusivities are only weakly dependent on this parameter. An estimate is given of the evolution of layer thickness with time in a semiconvective zone. The model predicts that the density ratio has a maximum for which a stationary layered state can exist, $R_ρ\la \mr{Le}^{-1/2}$. Comparison of the model predictions with a grid of numerical simulations is presented in a companion paper.
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