| 摘要 | 活动星系核的喷流是高能天体物理中的重要现象,对它的产生机制与能量来源的研究已成为现代天文学的热点之一,而这些喷流产生机制的模型大都与黑洞附近的磁层有关,因而研究黑洞磁层对于喷流的研究又有重要的意义。现代普遍认为,活动星系核的喷流的产生机制主要有三种:一是从旋转黑洞中提取转动能,称为Blandford-Znajek机制;二是BP机制;三是辐射压驱动的喷流模型。其中前两种都与磁场有直接的联系,而在黑洞附近由于磁场比较强,因而能够形成磁层,满足磁场的无力条件,人们都过对磁层的研究,进而能理解喷流等一些重要的高能天文现象。自从1977年Blandford与Znajek建立黑洞的无力磁层理论以来,寻找磁层的解析解就成为了人们的重要目标之一,由于方程的复杂性,使得这一问题的进展很缓慢,期间,人们只找到了几个微扰解和一个渐进解,寻找解析解可以更清晰的理解其直观图像,可以更好的理解物理过程。我在攻读硕士学位期间从一些角度尝试了去寻找解析解,这些尝试主要包括:(1)与李惠泉等人合作研究了近视界度规下的克尔黑洞无力磁层理论,建立了相应的基本方程并推导了边界条件,在视界附近,度规有较为简化的形式,而磁层的GS方程也有较为简洁的形式,利用这种形式,我们研究了旋转轴附近的解,发现当旋转角速度奇异时,可使解保持非奇异,这与Menon等人的结果是一致的。(2)考虑从黑洞提取能量取极值,即提取能量最有效,在这样的条件下我们做了研究,将三个未知函数中的两个联系了起来,并在一定条件下可以确定它们,同时还将GS方程化简为一阶拟线性偏微分方程,其特征方程是一个非常复杂的不定积分。(3)利用2005年Menon与Dermer得到的方程的形式,使用全微分条件,得到了一个新的联系?和Λ的方程,通过验证,以前的解都满足这个方程,我们的想法是将已经得到的解加以推广,进而研究更复杂的情况,这个工作还在进行之中。 |
| 其他摘要 | Black hole steady state force-free magnetosphere theories play an important role in the high energy astrophysics study, such as the emission mechanism of relativistic jets in Active Galactic Nuclei, Gamma-ray bursts and ultra-luminous X-ray binaries etc.In order to know the steady state force-free magnetospheres property,it’s need to find the solution of the Grad-Shafranov equation.Therefore, finding the analytic solutions of black hole steady state force-free magnetospheres is important significance for understanding these astronomical phenomena. In this paper, we first give a detailed review on this topic including the histories,recent progresses and future prospects,second,we give a discuss our works in near-NHEK force-free magnetospheres and other attempts. We first present the black hole electrodynamics and black hole force-free magnetosphere. We introduce the electromagnetic extraction of energy from Kerr black hole,the Blandford-Znajek mechanism and the black hole force-free magnetosphere in the aspect of application Active Galactic Nuclei relativistic jets and accretion disk. Next, we outline progress in solving the black hole steady state force-free magnetosphere equations in the part decades,including the solutions of Schwarzschild black hole,the perturbation solutions of low speed rotating black hole and the asymptotic solutions, we will give more discuss the asymptotic solutions.These solutions are important to study the black hole magnetosphere. We discuss the enlightment of these work on the analytic solution search efforts. Second,we will introduce the works in near-NHEK force-free magnetospheres and other attempts in study analytic solutions. In the near-NHEK space time,we develop the force-free magnetosphere theory and study the analytic solutions on axial. Finally, we study the solutions when the maximum energy density and other attempts appear. |
修改评论