黑洞磁化薄吸积盘的热稳定性  

Thermal Stability of Magnetized Thin Accretion Disks Around Black Holes

作　　者：郑圣明[1] 顾为民[1] 卢炬甫[1] 

机构地区：[1]厦门大学物理与机电工程学院,理论物理与天体物理研究所,福建厦门361005

出　　处：《厦门大学学报（自然科学版）》2011年第2期210-216,共7页Journal of Xiamen University：Natural Science

基　　金：国家重点基础研究发展计划(973)项目(2009CB824800);国家自然科学基金项目(10833002,11073015)

摘　　要：首先回顾了吸积盘理论产生的背景和研究概况.自从1991年Balbus和Hawley揭示了磁转动不稳定性(MRI)在较差转动流体系统中的重要性之后,磁场逐渐成为吸积盘理论研究所不可回避的成分.因此在标准薄盘模型的框架下,引入了环向磁场.假设在热扰动发生的时标内局部环向磁通量守恒,具体分析了当环向磁场参与到吸积盘垂向流体静力学平衡以及粘滞产热等过程之后,对盘的热稳定性所产生的影响.结果显示:当磁压在总压强中所占比例高于24%时,对任意的吸积率吸积盘都将呈现出热稳定性.这一结果有别于传统薄盘在辐射压主导情况下是热不稳定的结论,可以用于解释部分高光度X射线双星系统中缺少相应光变的观测事实,以及有助于理解近年来磁化吸积盘数值模拟中的一些结果.We briefly introduce the history of the development of accretion disk theories.Since Balbus Hawley first discovered the importance of MRI in differential rotating astrophysical systems in 1991,the magnetic field gradually becomes an unavoidable component in the study of accretion disk theory.We have included toroidal magnetic fields within the framework of standard accretion disk model.Assuming that the toroidal magnetic flux conserves during a thermal perturbation,we analyze the influence of the toroidal magnetic field,which contributes to the vertical hydrostatic equilibrium and the viscous heating,on the thermal stability of the disk in detail.Our results show that,when the ratio of magnetic pressure to total pressure exceeds 0.24,the disk would show thermal stability for any accretion rate.When the ratio is smaller,there also exist disk solutions that are radiation-pressure-dominated and meanwhile thermally stable.This is different from the conclusion drawn under the standard disk model that radiation-pressure-dominated solutions are always thermally unstable.Our new results can be applied in some luminous X-ray binaries that are lacking in variability on the thermal timescale,and may help understand the stability shown in some recent simulations of thin disks.

关 键 词：吸积盘 黑洞物理 不稳定性 

分 类 号：P142.6[天文地球—天体物理]