论文标题:天体物理吸积盘问题的研究
论文作者
论文导师 李晓卿；张航,论文学位 硕士,论文专业 天体物理
论文单位 南京师范大学,点击次数 120,论文页数 44页File Size1445K
论文网 http://www.lw23.com/lunwen_59834692/
accretion disks; anomalous viscosity; vertical structure ; hydrodynamics ;wave
两百多年前，天文科学家就开始了对吸积盘的讨论，吸积盘被认为在宇宙中广泛存在着，但直至最近，这一推断才被观测所证实。吸积盘的研究是天体物理中的重要问题，本文将从两个方面探讨关于吸积盘的问题，第一个问题是利用反常粘滞研究薄吸积盘的垂向结构，第二个是吸积盘中波的传播如何转移角动量的问题。 天体物理吸积盘是具有反常粘滞的流体盘，盘内物质的粘性比通常分子粘性高许多个数量级。我们利用磁吸积盘一种全新的反常粘滞结果(Li & Zhang2002)，研究了黑洞周围薄吸积盘的静态垂向结构。数值模拟得到了垂向结构上压力、温度、径向能流和物质密度在不同粘滞数值下的分布，与吸积盘标准模型(α模型)得到的结果相符合，这说明了Li和Zhang的磁塌缩机制引起的反常粘滞的有效性。 吸积盘中波的激发和传播能够转移角动量，二维的情况早在1979年Goldreich和Tremaine和1986年Ward的经典文章中讨论过，在这里我们把它推广到三维的情况。我们运用Tanaka，Takeuchi和Ward在2002年得到的三维盘的方程，通过利用傅立叶—厄米(Fourier-Hermite)展开，得到一个二阶的常微分方程，然后利用Goldreich和Tremaine的经典方法，我们得到了波在林德布拉德共振区激发的情况和角动量的传输率，把结果退化到二维的情况，发现结果与二维的结果是一致的。
Since about 200 years ago, astrophysicists have studied the accretion disks in the universe, they thought that disks are ubiquitous in astrophysics. Until recently, this deduction was testified by the observations. The study on accretion disks is very important in astrophysics. In this thesis , we will discuss two problems on accretion disks. One is using anomalous viscosity to discuss the stationary vertical structure of a thin disk around a black hole, the other is the wave excitation in a disk by external potential.It is well known that the astrophysical accretion disks are hydrodynamic disks with anomalous viscosity, the viscosity of matter in disks results in a factor of more amplification to the microscopic viscosity. Using the anomalous viscosity (Li &Zhang 2002), we discuss the stationary vertical structure of a thin disk around a black hole. These stationary vertical structures, including distributions of the pressure, temperature, radiative energy flux, mass density and radial velocities are examined. It is shown that the consideration of anomalous viscosity is necessary and the result is well conformed with the α standard prescription. It also proved that the anomalous viscosity is valid.The excitation of waves in disks by an external potential can translate augular momentum. Goldreich and Tremaine in 1979 and Ward in 1986 studied density wave excitation by an external potential in a 2D disk. In this paper, we will study the wave excitation in a 3D disk by external potentials, based on the formalism developed recently by Tanaka, Takeuchi and Ward in 2002. By taking advantage of Fourier-Hermite expansion, a second-order differential equation for a distinct mode is attained. Then, following the standard technique used by Goldreich and Tremaine in 1979, the simplified equations are solved and analytic expressions for the waves excited at various locations and associated augular momentum transfer rate are manifested. It is noted that when we draw it back to 2D conditions, our result is the same as that for the 2D non-self-gravitating case.
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