吸积盘中的反常磁黏滞及其应用

发布时间：2018-04-13 20:12

本文选题：吸积盘 + 自生磁场　；参考：《南昌大学》2013年博士论文

【摘要】：早在上世纪二十年代,吸积盘理论就被用于研究太阳星云的形成及演化,1969年,Lynden-Bell开创性地利用该理论解释了类星体的能源机制,使得吸积盘理论的应用得到突破性进展。时至今日,吸积盘理论依然是等离子体天体物理研究的热点课题之一。从物理学角度来讲,吸积盘的形成存在两个重要的物理过程：物质向内吸积以及角动量向外转移。盘的结构与演化依赖于角动量的转移,而盘中黏滞的大小及其性质正是决定角动量转移的重要因素。换言之,吸积盘的结构及其演化取决于盘中的黏滞。然而,纯粹的分子黏滞不可能实现吸积盘中角动量转移过程,吸积盘非常可能处于湍动状态。上世纪七十年代,Shakura与Sunyaev引入湍动黏滞的概念,并建立标准薄盘模型,亦称SSD模型,使得吸积盘理论由过去的定性及半定量描述上升到定量描述的理论高度。然而SSD模型是一个参量化的唯象模型,它掩盖了湍动黏滞的本质,人们无法从中得到更多有关湍动的信息。因此,天体物理学家必须寻找一种能够揭示湍动黏滞物理本质的新模型。 2002年,李晓卿和张航从动力论出发,考虑到波-波、波-粒相互作用,理论计算得到非相对论性等离子体中横等离激元产生的低频自生磁场方程。调制不稳定性分析表明这种磁场具有大的不稳定性增率,能够坍塌到局域小尺度范围内,形成空间高度间歇的强磁流,呈现湍动状态。这些强磁流元之间以及磁流元与周围介质之间的相互作用是吸积盘中反常黏滞产生的本质。本论文首先利用这种新的反常磁黏滞机制,分别研究了年轻恒星周围磁化薄吸积盘以及原恒星盘的结构与不稳定性。结果表明,利用反常黏滞模型能够得到与观测相吻合的温度分布及更接近真实的盘结构,这使得稳定性分析更有意义。本论文研究内容之二是基于李晓卿等人得到的相对论性等离子体中自生磁场非线性控制方程,找到自生磁场的自类似坍塌解；从间歇磁流间相互作用的麦克斯韦应力张量出发,把反常黏滞理论推广至相对论框架,理论推导得到相对论性吸积盘中的反常磁黏滞运动学系数。结果表明,相对论性吸积盘中的反常黏滞系数对电子有效温度的依赖关系与非相对论中的情况截然不同。其三,对李晓卿等人引力横等离激元相互作用产生自生甚低频磁型引力场耦合方程进行调制不稳定性分析。分析表明,自生引力磁场是调制不稳定的,并通过数值拟合计算出调制不稳定性最大增长率及对应的最大波数,找到引力磁场坍塌的自类似解；理论计算得到自引力吸积盘中的反常磁黏滞运动学系数；与分子黏滞比较发现,反常磁黏滞强于分子黏滞约八个量级,足以提供自引力盘中物质吸积及角动量转移所需的吸积率,这与文献中给出的结果相吻合。吸积盘中反常磁黏滞模型明确揭示了湍动黏滞产生的物理机制,有助于研究天体物理吸积盘中非线性过程；同时也为实验和模拟提供理论指导。
[Abstract]:In the early 20s, the accretion disk theory has been used to study the formation and evolution of the solar nebula, 1969, Lynden-Bell creatively use the theory to explain the energy mechanism of quasars, the application of accretion disk theory has a breakthrough. Today, the accretion disk theory is still one of the hot research topics in plasma astrophysics from the physics point of view, the formation of an accretion disk has two important processes: material inward accretion and angular momentum outwards. The structure and evolution of the disk transfer depends on the angular momentum, and the size and nature of plate stick lag is an important factor that decides the transfer of angular momentum. In other words, the structure of accretion the disc and its evolution depends on the disc viscosity. However, pure molecular viscosity can not be achieved in accretion disks, angular momentum transfer process, the accretion disk may be in very turbulent state. In 70s, Shakura and Sunyaev introduced the concept of turbulent viscosity, and the establishment of the standard thin disk model, called SSD model, and by semi quantitative qualitative description of the past to rise to the level of theory makes the quantitative description of the accretion disk theory. However, the SSD model is a parametric phenomenological model, it obscures the nature of turbulence the dynamic viscosity, people can get more information about the turbulence from it. Therefore, astrophysicists have to search for a new model to reveal the physical nature of the turbulent viscosity.
In 2002, Li Xiaoqing and Zhang hang from the view of power, taking into account the wave wave and wave particle interaction, calculated the non relativistic low frequency transverse plasma plasmons generated spontaneous magnetic field equation. The analysis shows that this magnetic field has increased rate of instability of modulation instability can be collapsed into local small scale range, strong magnetic forming highly intermittent flow, showing the turbulent state. The strong magnetic element between the flow and magnetic interaction between the element and the surrounding medium is the essence of the accretion disks of anomalous viscosity produced. Firstly, using the new anomalous magnetic viscosity mechanism, and instability of structure are studied the magnetization of thin accretion disks around young stars and a protostellar disk. The results show that the anomalous viscosity model can obtain the temperature distribution is consistent with the observations and more close to the real plate structure, which makes the stability of points It is more meaningful to analyze.
The content of this paper is the two magnetic field nonlinear equations of authigenic relativistic plasma obtained by Li Xiaoqing et al found based on self generated magnetic field self similar collapse solution; starting from the Maxwell stress tensor intermittent flux interactions, the anomalous viscosity theory extends to the relativistic framework, the theoretical derivation of anomalous magnetic relativity the viscosity of the accretion disk kinematics coefficient. The results show that the dependence of anomalous viscosity coefficient of relativistic accretion disk on the electron effective temperature and non relativity in different situation.
Third, analysis of authigenic VLF magnetic gravitation field coupling equation of modulation instability of Li Xiaoqing gravity transverse plasmons interaction. Analysis shows that the gravitational field is self modulation instability, and through numerical fitting to calculate the maximum modulation instability wave number maximum growth rate and the gravitational collapse of the magnetic field is found the self similar solution; calculated the anomalous magnetic self gravitating accretion disk kinematics viscosity coefficient; and molecular viscosity comparison found that the anomalous magnetic viscosity is stronger than the molecular viscosity of about eight orders of magnitude, enough to provide the required material from the accretion disk accretion and the gravitational angular momentum transfer rate, which is consistent with the literature the results given in.
The anomalous magnetic viscosity model in accretion disk clearly reveals the physical mechanism of turbulent viscous generation, and helps to study the nonlinear process in astrophysical accretion disks. It also provides theoretical guidance for experiments and simulations.

【学位授予单位】：南昌大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P142

【参考文献】