本文關(guān)鍵詞： 原行星盤 不透明度 盤子結(jié)構(gòu)　出處：《吉林大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：現(xiàn)有理論認為，行星在原行星盤中形成。原行星盤的形成和演化對行星的形成至關(guān)重要，是研究的熱點。分子云核塌縮過程中，由于具有角動量，物質(zhì)沒有完全掉落到中央恒星，而是在恒星周圍形成扁平的原行星盤。原行星盤主要由氣體組成，在粘滯的作用下角動量重新分布。物質(zhì)向內(nèi)流向中央恒星，少部分物質(zhì)由于角動量守恒向外流動。 對于圍繞類似太陽的中央恒星的薄盤，一般用面密度來描述原行星盤的演化。其他的物理量還有溫度、盤厚、粘滯系數(shù)、和穩(wěn)定性等。當(dāng)面密度一定時，其他物理量可以寫為面密度的函數(shù)。對盤子演化很重要的物理量是粘滯系數(shù)，粘滯系數(shù)與溫度相關(guān)，而溫度與原行星盤的不透明度相關(guān)。因此采取什么樣的不透明度對盤子有什么樣的影響，是很重要的。 不透明度的研究有數(shù)值的研究，也有理論的擬合，在不同的文章里用到過不同的擬合公式。不透明度是溫度的分段函數(shù)。為了得到不同不透明度對盤子演化的影響，我們?nèi)×怂膫�不同不透明度的分析公式，來比較盤子的演化。 對于盤子的形成，我們用JinSui(2010)的盤子演化模型。盤子由分子云核塌縮而來。為了顯示不透明度的影響，四種情況中，我們選擇了相同的分子云核參數(shù)，也是觀測給出的參數(shù)值。分子云核質(zhì)量取1M⊙，溫度取15K。轉(zhuǎn)動角速度取0.31014s-1，是觀測的最小值，粘滯取1104。金屬豐度取太陽系的值。 我們研究了原行星盤面密度、溫度、以及不穩(wěn)定性和不透明度的關(guān)系。我們使用了BellLin (1994)、Bell et al.(1997)、NakamotoNakagawa (1994)、以及RudenLin (1986)的不透明度。結(jié)果顯示，不透明度相似時，各物理量的變化不大。說明這些物理量對不透明度的依賴不敏感。而取很簡單的不透明度時，在原行星盤的小半徑區(qū)域，，各物理量有顯著的變化。簡單的不透明度使小半徑區(qū)域面密度下降、溫度升高、穩(wěn)定性增強。 四種不透明度情況下，原行星盤在整個演化過程中都是穩(wěn)定的。這主要是由于我們選擇了小的分子云核初始轉(zhuǎn)動角速度。當(dāng)取大的轉(zhuǎn)動角速度時，不透明度的不同形式有可能改變盤子的穩(wěn)定性。 盡管不透明度對盤子結(jié)構(gòu)和演化有影響，但盤子演化依然有不變的特征。如在分子云核塌縮結(jié)束后，孤盤演化過程中，面密度在小半徑區(qū)域隨時間減小，在大半徑區(qū)域增大，溫度則是都減小，Q參數(shù)的最小值隨時間增大。隨半徑的變化是：面密度、溫度隨半徑減小，Q參數(shù)隨半徑先減小，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.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P15

【共引文獻】

相關(guān)博士學(xué)位論文 前1條

1 藺福軍;吸積盤中的反常磁黏滯及其應(yīng)用[D];南昌大學(xué);2013年

本文編號：1443425