磁化吸积盘：致密天体高能辐射及喷流的中心发动机
发布时间：2019-07-06 08:20
【摘要】： 黑洞是广义相对论的一个重要的预言。现在人们已经普遍相信,几乎在每一个星系中央都存在着一个超大质量黑洞。以黑洞为核心的致密天体,包括活动星系核和某些X射线双星、伽玛射线暴等,展现出了一些非常极端的高能辐射现象,并时常伴随着猛烈的喷流和复杂的光变。 黑洞吸积是这些致密天体“中心发动机”事实上的标准模型。经过几十年的发展,吸积盘理论日趋完善,但也存在着一些基本的问题尚无定论,如粘滞的物理过程、盘上外流的发生机制等。近年来,人们逐渐意识到磁场可能在物质吸积的过程中扮演着非常重要的角色,其中包括小尺度和大尺度两种形态的磁场。前者对应于吸积流内部的粘滞过程以促使吸积的进行,如“磁旋转不稳定性”(MRI)；后者则被认为与喷流的加速、准直以及宏观的能量、角动量转移相关,如Blandford-Payne(BP)过程。 除吸积外,快速旋转的黑洞其本身也是一个巨大的能源。在本文中我们详细地阐述了通过大尺度磁场从黑洞提取能量的物理机制,包括Blandford-Znajek (BZ)过程和磁耦合(Magnetic Coupling, MC)过程。本文细致地论述了MC过程中的能量转移及其在盘内部耗散的过程、MC过程对吸积盘辐射特征的影响、MC过程对吸积盘位形的影响——由于MC过程导致的盘内边缘位置的移动。 考虑到大尺度闭合磁场对等离子体的束缚作用,我们提出了一个“磁化吸积盘—冕”模型。其中,MC过程的大尺度磁场很自然地为冕物质提供了一个落向黑洞视界面的通道,籍此我们得以限制冕的分布。通过综合求解黑洞与吸积盘、吸积盘与冕之间的能量传递及其对盘动力学和磁场分布的影响,我们自洽地得到了盘冕系统的整体解,并用Monte-Carlo方法模拟了系统的出射谱。结果表明,盘冕系统很自然地具有“高光度、软谱态”或者“低光度、硬谱态”的辐射特征,这一特性可用于解释一些黑洞双星的高能X射线非热谱。 另外,越来越多的观测证据表明,喷流与吸积之间存在着密切的联系。我们从能量和角动量平衡的角度出发论述了磁化外流与吸积盘之间的耦合。盘上发出的外流将降低吸积盘的光度,而吸积盘的动力学性质反过来也限制着对外流的功率输出。籍此我们解释了一些射电类星体盘光度与喷流功率的相关关系。另外,考虑到外流可以有效地带走角动量,我们讨论了通过磁化外流解决吸积盘角动量整体平衡的可能性。 在我们的模型中,黑洞自转的快慢和大尺度磁场位形至关重要。最后我们对这两个问题进行了讨论,并期望日后能够找到一些观测上的判别。 作为攻读博士学位期间的学习和工作总结,结合自己的理解本文引述了较多的理论背景知识。作者本人的工作主要分布在第2.3、2.4、3.2、4.2、4.3和5.1节,感兴趣的读者可直接跳读到相关的章节。
文内图片：
图片说明：1黑洞x射线双星的吸积和喷流(艺术想象图)
[Abstract]:Black holes are an important prophecy of general relativity. It is now widely believed that there is a supermassive black hole in the center of almost every galaxy. Dense celestial bodies with black holes as the core, including active galactic nucleus and some X-ray binary stars, gamma-ray bursts, show some very extreme high-energy radiation phenomena, and are often accompanied by violent jet and complex light changes. Black hole accretion is the de facto standard model of the central engine of these dense celestial bodies. After decades of development, the theory of accretion disk is becoming more and more perfect, but there are still some basic problems, such as viscous physical process, the occurrence mechanism of disk outflow and so on. In recent years, it has been gradually realized that magnetic fields may play a very important role in the process of material accretion, including small-scale and large-scale magnetic fields. The former corresponds to the viscous process in the accretion flow to promote the accretion, such as "magnetic rotation instability" (MRI);, the latter is considered to be related to the acceleration, collimation, macroscopic energy and angular momentum transfer of the jet, such as the Blandford-Payne (BP) process. In addition to accretion, the fast-rotating black hole itself is a huge source of energy. In this paper, we describe in detail the physical mechanism of extracting energy from black holes through large-scale magnetic fields, including Blandford-Znajek (BZ) process and magnetic coupling (Magnetic Coupling, MC) process. In this paper, the energy transfer and its dissipation in MC process, the influence of MC process on the radiation characteristics of accretion disk and the influence of MC process on the configuration of accretion disk are discussed in detail. The movement of edge position in disk caused by MC process is also discussed in detail. Considering the binding effect of large-scale closed magnetic field on plasma, we propose a "magnetized accretion disk-corona" model. Among them, the large-scale magnetic field of MC process naturally provides a channel for coronal matter to fall to the apparent interface of black hole, so that we can limit the distribution of corona. By solving the energy transfer between black hole and accretion disk, accretion disk and corona and their influence on disk dynamics and magnetic field distribution, we obtain the global solution of disk coronal system and simulate the ejection spectrum of the system by Monte-Carlo method. The results show that the disk coronal system naturally has the radiation characteristics of "high luminance, soft spectral state" or "low luminance, hard spectral state", which can be used to explain the high energy X-ray non-thermal spectra of some black hole binary stars. In addition, more and more observational evidence shows that there is a close relationship between jet and accretion. From the point of view of energy and angular momentum balance, we discuss the coupling between magnetization outflow and accretion disk. The outflow from the disk will reduce the luminance of the accretion disk, and the dynamic properties of the accretion disk in turn limit the power output to the outflow. In this paper, we explain the correlation between the disk luminance of some radio quasars and jet power. In addition, considering that the outflow can effectively take away the angular momentum, we discuss the possibility of solving the global equilibrium of the angular momentum of the accretion disk by magnetization outflow. In our model, the speed of black hole rotation and the configuration of large-scale magnetic field are very important. Finally, we discuss these two problems and hope to find some observational discrimination in the future. As a summary of the study and work during the doctoral degree, combined with my own understanding, this paper quotes more theoretical background knowledge. The author's own work is mainly distributed in sections 2.3, 2.4, 3.2, 4.2, 4.3 and 5.1. Interested readers can skip to the relevant chapters.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：P145.8
本文编号：2510896
文内图片：
图片说明：1黑洞x射线双星的吸积和喷流(艺术想象图)
[Abstract]:Black holes are an important prophecy of general relativity. It is now widely believed that there is a supermassive black hole in the center of almost every galaxy. Dense celestial bodies with black holes as the core, including active galactic nucleus and some X-ray binary stars, gamma-ray bursts, show some very extreme high-energy radiation phenomena, and are often accompanied by violent jet and complex light changes. Black hole accretion is the de facto standard model of the central engine of these dense celestial bodies. After decades of development, the theory of accretion disk is becoming more and more perfect, but there are still some basic problems, such as viscous physical process, the occurrence mechanism of disk outflow and so on. In recent years, it has been gradually realized that magnetic fields may play a very important role in the process of material accretion, including small-scale and large-scale magnetic fields. The former corresponds to the viscous process in the accretion flow to promote the accretion, such as "magnetic rotation instability" (MRI);, the latter is considered to be related to the acceleration, collimation, macroscopic energy and angular momentum transfer of the jet, such as the Blandford-Payne (BP) process. In addition to accretion, the fast-rotating black hole itself is a huge source of energy. In this paper, we describe in detail the physical mechanism of extracting energy from black holes through large-scale magnetic fields, including Blandford-Znajek (BZ) process and magnetic coupling (Magnetic Coupling, MC) process. In this paper, the energy transfer and its dissipation in MC process, the influence of MC process on the radiation characteristics of accretion disk and the influence of MC process on the configuration of accretion disk are discussed in detail. The movement of edge position in disk caused by MC process is also discussed in detail. Considering the binding effect of large-scale closed magnetic field on plasma, we propose a "magnetized accretion disk-corona" model. Among them, the large-scale magnetic field of MC process naturally provides a channel for coronal matter to fall to the apparent interface of black hole, so that we can limit the distribution of corona. By solving the energy transfer between black hole and accretion disk, accretion disk and corona and their influence on disk dynamics and magnetic field distribution, we obtain the global solution of disk coronal system and simulate the ejection spectrum of the system by Monte-Carlo method. The results show that the disk coronal system naturally has the radiation characteristics of "high luminance, soft spectral state" or "low luminance, hard spectral state", which can be used to explain the high energy X-ray non-thermal spectra of some black hole binary stars. In addition, more and more observational evidence shows that there is a close relationship between jet and accretion. From the point of view of energy and angular momentum balance, we discuss the coupling between magnetization outflow and accretion disk. The outflow from the disk will reduce the luminance of the accretion disk, and the dynamic properties of the accretion disk in turn limit the power output to the outflow. In this paper, we explain the correlation between the disk luminance of some radio quasars and jet power. In addition, considering that the outflow can effectively take away the angular momentum, we discuss the possibility of solving the global equilibrium of the angular momentum of the accretion disk by magnetization outflow. In our model, the speed of black hole rotation and the configuration of large-scale magnetic field are very important. Finally, we discuss these two problems and hope to find some observational discrimination in the future. As a summary of the study and work during the doctoral degree, combined with my own understanding, this paper quotes more theoretical background knowledge. The author's own work is mainly distributed in sections 2.3, 2.4, 3.2, 4.2, 4.3 and 5.1. Interested readers can skip to the relevant chapters.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：P145.8
【参考文献】
相关期刊论文 前1条
1 卢炬甫;黑洞吸积盘理论进展[J];天文学进展;2001年03期
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