不透明度对原行星盘结构的影响

发布时间：2018-01-19 08:27

本文关键词： 原行星盘不透明度盘子结构　出处：《吉林大学》2014年硕士论文　论文类型：学位论文

【摘要】：现有理论认为，行星在原行星盘中形成。原行星盘的形成和演化对行星的形成至关重要，是研究的热点。分子云核塌缩过程中，由于具有角动量，物质没有完全掉落到中央恒星，而是在恒星周围形成扁平的原行星盘。原行星盘主要由气体组成，在粘滞的作用下角动量重新分布。物质向内流向中央恒星，少部分物质由于角动量守恒向外流动。对于围绕类似太阳的中央恒星的薄盘，一般用面密度来描述原行星盘的演化。其他的物理量还有温度、盘厚、粘滞系数、和稳定性等。当面密度一定时，其他物理量可以写为面密度的函数。对盘子演化很重要的物理量是粘滞系数，粘滞系数与温度相关，而温度与原行星盘的不透明度相关。因此采取什么样的不透明度对盘子有什么样的影响，是很重要的。不透明度的研究有数值的研究，也有理论的拟合，在不同的文章里用到过不同的拟合公式。不透明度是温度的分段函数。为了得到不同不透明度对盘子演化的影响，我们取了四个不同不透明度的分析公式，来比较盘子的演化。对于盘子的形成，我们用JinSui(2010)的盘子演化模型。盘子由分子云核塌缩而来。为了显示不透明度的影响，四种情况中，我们选择了相同的分子云核参数，也是观测给出的参数值。分子云核质量取1M⊙，温度取15K。转动角速度取0.31014s-1，是观测的最小值，粘滞取1104。金属丰度取太阳系的值。我们研究了原行星盘面密度、温度、以及不稳定性和不透明度的关系。我们使用了BellLin (1994)、Bell et al.(1997)、NakamotoNakagawa (1994)、以及RudenLin (1986)的不透明度。结果显示，不透明度相似时，各物理量的变化不大。说明这些物理量对不透明度的依赖不敏感。而取很简单的不透明度时，在原行星盘的小半径区域，，各物理量有显著的变化。简单的不透明度使小半径区域面密度下降、温度升高、稳定性增强。四种不透明度情况下，原行星盘在整个演化过程中都是稳定的。这主要是由于我们选择了小的分子云核初始转动角速度。当取大的转动角速度时，不透明度的不同形式有可能改变盘子的稳定性。尽管不透明度对盘子结构和演化有影响，但盘子演化依然有不变的特征。如在分子云核塌缩结束后，孤盘演化过程中，面密度在小半径区域随时间减小，在大半径区域增大，温度则是都减小，Q参数的最小值随时间增大。随半径的变化是：面密度、温度随半径减小，Q参数随半径先减小，后增大。
[Abstract]:The existing theory holds that the planets are formed in the original planetary disk. The formation and evolution of the protoplanetary disk are very important for the formation and evolution of the planet, which is a hot topic of research. In the process of collapse of the molecular cloud nucleus, the formation and evolution of the original planetary disk is due to the angular momentum. Instead of falling completely into the central star, matter forms a flat planet-disk around the star. The protoplanetary disk is composed mainly of gases, and angular momentum is redistributed under viscous action. Matter flows inward to the central star. A small portion of matter flows outwards due to the conservation of angular momentum. The surface density is generally used to describe the evolution of the original planetary disk for the thin disk around a central star similar to the sun. Other physical quantities include temperature, disk thickness, viscosity coefficient, stability, and so on. Other physical quantities can be written as a function of surface density. The important physical quantity for plate evolution is the viscosity coefficient, which is related to temperature. The temperature is related to the opacity of the original planetary disk. So what kind of opacity will affect the plate is important. The study of opacity includes numerical study and theoretical fitting. Different fitting formulas have been used in different articles. Opacity is a piecewise function of temperature. In order to get the effect of different opacity on plate evolution, we have taken four different opacity analysis formulas. To compare the evolution of plates. For plate formation, we use Jin Sui 2010's plate evolution model, which collapses from molecular cloud nuclei. In order to show the effect of opacity, in four cases. We have chosen the same molecular cloud kernel parameters, which are also the observed values. The molecular cloud nucleus mass is 1 M}, the temperature is 15 K, and the rotational angular velocity is 0.310 14 s -1, which is the minimum observed value. Viscosity takes 1104. Metal abundance takes the value of the solar system. We have studied the relationship between the surface density, temperature, instability and opacity of the protoplanetary disk. We have used BellLin 1994 / Bell et al. 1997). NakamotoNakagawa / 1994, and RudenLin / 1986) opacity. The results show that the opacity is similar when the opacity is similar. It is shown that these quantities are insensitive to opacity. In the case of simple opacity, they are in the small radius of the original planetary disk. The simple opacity decreases the surface density of the small radius region, increases the temperature and enhances the stability. In the four opacity cases, the original planetary disk is stable throughout the evolution process. This is mainly due to the selection of the initial rotation angular velocity of the small molecular cloud nuclei. Different forms of opacity may change the stability of the plate. Although opacity has an effect on the structure and evolution of the plate, the plate evolution still has the same characteristics. For example, after the collapse of the molecular cloud nucleus, the surface density in the small radius region decreases with time during the solitary disk evolution. In the region of large radius, the minimum value of temperature decreases with time, and the change of temperature with radius is as follows: surface density, temperature decreases with radius, Q parameter decreases with radius, and then increases with radius.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P15

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