含平流双温吸积盘的振荡不稳定性研究

从流体动力学方程出发,用微扰法得出含平流双温吸积盘的径向,环向不稳定性的色散方程,并对平流和径向粘滞力对双温吸积盘的影响进行了较详细的讨论。结果表明：平流和径向粘滞力对声模有较大的影响,且不改变粘滞模和热模的稳定性质。而环向扰动对吸积盘的各种模有着较明显的作用,这一模型有利于解释活动天体的周期和准周期光变现象。     

磁化吸积盘的不稳定性研究

从磁流体动力学方程组出发,用微扰法得到的色散方程中含有环向磁场.利用全新的反常粘滞和反常阻抗,对吸积盘进行数值计算,结果表明,只有竖直方向的弱磁场才可以引发一种单调不稳定性.磁场对粘性吸积盘表现为非稳定性因素,增长率随磁场的增强而增大,且最大增长率大于理想情况下的值.垂向磁场足够强时,单调不稳定性不会出现.     

含三维磁场等温薄吸积盘的振荡不稳定性

本从磁流体动力学方程组出发,用微扰法得出含三维磁场等温薄吸积盘的径向,轴向及环向不稳定性的色散方程,并详细讨论了磁场各分量对吸积盘不稳定性的影响。结果表明,磁场的径向和环向分量对磁场声模和非轴对称模的不稳定性的增加起着主要的作用,且径向振荡大于轴向振荡,这一模型有利于解释ＦＵＯｒｉｏｎｉｓ和ＴＴａｕｒｉＳｔａｒｓ的周期光变现象。     

含粘滞和磁场的薄吸积盘不稳定性

本文采用微扰方法导出色散方程，并在四种情况下详细讨论了薄吸积盘的不稳定性，结果表明：在纯粘滞和纯磁场盘中存在脉动不稳定性，而且在吸积盘内同时考虑粘滞和磁场时，存在两稳定性，一种是脉动不稳定性，另一种是单调不稳定性，同时数值计算否定有明，脉动不稳定性更可能存在于内区，而财不稳定性则只在盘的外区，对短波扰动才有意义，这些结果为解释ＢＬ Ｌａｃ天体、Ｓｅｙｆｅｒｔ星系及星体活动星系核的光变现象进一步提供     

含三维磁场等温薄吸积盘的振荡不稳定性

本文从磁流体动力学方程组出发,用微扰法得出含三维磁场等温薄吸积盘的径向、轴向及环向不稳定性的色散方程．并详细讨论了磁场各分量对吸积盘不稳定性的影响．结果表明,磁场的径向和环向分量对磁声模和非轴对称模的不稳定性的增加起着主要的作用,且径向振荡大于轴向振荡．这一模型有利于解释ＦＵＯｒｉｏｎｉｓ和ＴＴａｕｒｉＳｔａｒｓ的周期光变现象     

含粘滞和磁场的薄吸积盘不稳定性

本文采用微扰方法导出色散方程，并在四种情况下详细讨论了薄吸积盘的不稳定性。结果表明：在纯粘滞和纯磁场盘中都存在脉动不稳定性。而且在吸积盘内同时考虑粘滞和磁场时，存在两种不稳定性，一种是脉动不稳定性，另一种是单调不稳定性。同时数值计算还表明，脉动不稳定性更可能存在于盘的内区，而单调不稳定性则只在盘的外区，对短波扰动才有意义。这些结果为解释ＢＬＬａｃ天体、Ｓｅｙｆｅｒｔ星系及类星体等活动星系核的光变现象进一步提供了理论依据。     

含平流（avdection）的热单温吸积流的径向结构

本在小粘滞参数，低吸积率的条件下，借助含平流的热吸积流的自相似解，考虑非热正负电子对产生，采用分两个区域分别求妥然后对接的方法，研究了含平流的热单温吸积流的径向结构。证实了热吸积流所具有的一些显特征和基本性质，同时得到一些新的结果：含平流的热吸积流存在一个临界半径ｒＣｒ；明确指 出含平流的热吸积流的辐射冷却率与中心天体的质量成平方反比关系；提出正负电子对过程对含平流的热吸积流的辐射过程有显影     

含粘滞性弱磁化吸积盘的轴对称脉动不稳定性

本文讨论了一种含扩散型粘滞的弱磁化等温吸积盘模型，在此模型中研究了扩散型粘滞、垂向磁场Bz和环向磁场B对轴对称脉动不稳定性的影响．结果表明，对于轴对称扰动，一般情况下盘内存在四种轴对称振荡模式．其中二种模式是脉动不稳定的，粘滞和磁场对它们表现为非稳因素；而另外二种模式是稳定的，粘滞和磁场对它们表现为致稳因素．此外我们还注意到，Bz和B主要影响近轴向的脉动不稳定性，扩散型弱粘滞主要影响径向脉动不稳定性．     

含粘滞的弱磁化吸积盘的非轴对称脉动不稳定性

本文讨论了一种含扩散型粘滞的弱磁化等温吸积盘模型．在作者原有工作的基础上研究了吸积盘对非轴对称扰动（含径向、环向和垂向三个方向的扰动）所表现的脉动不稳定性．结果表明，径向扰动是最重要、最根本的扰动：在无径向扰动时，吸积盘中不存在环向扰动与垂向扰动所产生的脉动不稳定性．在径向扰动存在时，吸积盘除了可能存在纯径向脉动不稳定性外，还可能存在由于径向扰动与垂向扰动的耦合所引起的轴对称脉动不稳定性，以及由于径向扰动与环向扰动的耦合所引起的非轴对称脉动不稳定性．当上述三个方向的扰动并存时，对应的非轴对称脉动不稳定性也可能存在．     

对等温、有磁薄吸积盘脉动不稳定性的多因素影响

本文从磁流体动力学方程组出发，用微扰法得出等温有磁薄吸积盘径向脉动不稳定性的色散方程，详细讨论了磁场、径向粘滞力和因果性修正的α型粘滞对吸积盘不稳定性的影响．我们的结论是：磁场是一种在全盘区域起作用的非稳因素，它能影响粘滞模式的不稳定性和两种声波模式（O－mode和Ⅰ－mode）的增长率．径向粘滞力是一种在全盘区域起作用的致稳因素，它主要影响两种声波模式的不稳定性．α型粘滞的因果性修正主要在盘内区起作用，它对吸积盘的不稳定性影响较为复杂：对粘滞模式和无磁盘的Ⅰ-mode，它表现为致稳因素，而对O－mode和有磁盘的两种声波模式，则表现为非稳因素．     

Accretion disc outbursts: a new version of an old model

We have developed 1D time-dependent numerical models of accretion discs, using an adaptive grid technique and an implicit numerical scheme, in which the disc size is allowed to vary with time. The code fully resolves the cooling and heating fronts propagating in the disc. We show that models in which the radius of the outer edge of the disc is fixed produce incorrect results, from which probably incorrect conclusions about the viscosity law have been inferred. In particular we show that outside-in outbursts are possible when a standard bimodal behaviour of the Shakura–Sunyaev viscosity parameter α is used. We also discuss to what extent insufficient grid resolution has limited the predictive power of previous models. We find that the global properties (magnitudes, etc.) of transient discs can be addressed by codes using a high, but reasonable, number of fixed grid points. However, the study of the detailed physical properties of the transition fronts generally requires resolutions which are out of reach of fixed grid codes. It appears that most time-dependent models of accretion discs published in the literature have been limited by resolution effects, improper outer boundary conditions, or both.     

径向粘滞力对薄盘稳定性的影响

在吸积盘内由于吸积物质的径向运动，盘内物质间沿径向的粘滞力将会对盘的性质产生一定影响．本文计算了等温吸积盘中（考虑径向粘滞力）的不稳定性问题，对所求得的色散方程的分析表明，径向粘滞力将使吸积盘趋向稳定。本文还对径向粘滞力对盘的稳定性的影响作了物理解释，并发现径向粘滞力的引入不会引入新的稳定或不稳定模式。     

Long-term nonlinear behaviour of the magnetorotational instability in a localized model of an accretion disc

For more than a decade, the so-called shearing-box model has been used to study the fundamental local dynamics of accretion discs. This approach has proved to be very useful because it allows high-resolution and long-term studies to be carried out, studies that would not be possible for a global disc.
Localized disc studies have largely focused on examining the rate of enhanced transport of angular momentum, essentially a sum of the Reynolds and Maxwell stresses. The dominant radial–azimuthal component of this stress tensor is, in the classic Shakura–Sunyaev model, expressed as a constant α times the pressure. Previous studies have estimated α based on a modest number of orbital times. Here we use much longer baselines, and perform a cumulative average for α. Great care must be exercised when trying to extract numerical α values from simulations: dissipation scales, computational box aspect ratio, and even numerical algorithms can all affect the result. This study suggests that estimating α becomes more, not less, difficult as computational power increases.     

黑洞吸积盘内区温度的分布特征和演化特征

对黑洞吸积盘内区温度的径向分布特征和演化特征作了详细的讨论．结果表明：（１）盘内区的温度并非随径向坐标ｒ单调减少,在接近盘的内边缘处有一个盘温的峰值环．在盘温的峰值环和盘的内边缘之间形成一个温度梯度很大的冷却区;（２）在盘吸积的过程中,盘内区温度的峰值和冷却区的平均温度梯度均随中心黑洞的无量纲角动量ａ的增加而单调增加,而金温峰值环半径和冷却区的径向宽度均随ａ的增加而单调减小;（３）盘的热辐射光度随ａ的增加而单调增加．     

Thermal conduction between an accretion disc and a corona in active galactic nuclei: vertical structure of the transition layer

We study the vertical structure of the transition layer between an accretion disc and a corona in the context of the existence of a two-phase medium in thermally unstable regions. The disc is illuminated by hard X-ray radiation, and satisfies the condition of hydrostatic equilibrium. We take into account the energy exchange between the hot, Compton-heated corona (∼10⁸ K) and cool disc (∼10⁴ K) arising from both radiative processes and thermal conduction. In the case including thermal conduction, we perform a local stability analysis, and conclude that thermal conduction does not suppress thermal instability. In spite of the continuous temperature profile T ( τ ) there are regions of strong temperature gradient, in which spontaneous perturbations can lead to cloud condensation in the transition layer. We determine the minimum size λ _TC of such a perturbation.