Structure and Stability of Advection-Dominated Accretion Disks

1)平流主导型吸积盘的构建在与E.Narayan教授合作构建了单温度平流主导型吸积盘模型之后，我们继续构建双温度平流主导型吸积盘模型。首先，我们制作了这样的圆盘模型，只把轫致辐射作为电子气体的冷却过程。在此成功之后，我们构建了更一般的模型，将康普顿过程和同步加速器过程考虑为电子气体的冷却过程。平流主导型吸积盘的热不稳定性研究平流主导型吸积盘的热不稳定性对于理解x射线恒星和活动星系核的时间变化的起源具有重要意义。由于以平流为主的圆盘在垂直方向上相对较厚，因此应采用不同于标准圆盘的方法来研究它们的热不稳定性。我们的分析表明，如果湍流热传导可以忽略不计，以平流为主的吸积盘对局部扰动是弱不稳定的。非磁化开普勒盘的湍流。开普勒盘对轴对称扰动具有高度的稳定性（瑞利准则）。从这个意义上说，通常假定磁场是使圆盘产生湍流（巴尔布斯-霍利不稳定性）所必需的。我们认为这种说法并不总是正确的，并构建了一个可能的开普勒盘流体动力学湍流模型。

1)Construction of Advection-Dominated Accretion DisksAfter having constructed one-temperature advection-dominated disk models in collaboration with Prof. E.Narayan, we proceeded to make two-temperature advectiondominated disk models. First we made such disk models, taking only bremsstrahlung as cooling processes of electron gas. After this success, we constructed more general models, taking Compton and synchrotron processes into account as cooling processes of electron gas.2)Thermal Instability of Advection-Dominated Accretion DisksExamination of thermal instability of advection-dominated disks is of importance in relation to understanding origins of time variations of X-ray stars and active galactic nulei. Since advection-dominated disks are relatively thick in the vertical direction, their thermal instability should be studied by a method different from that used for standard disks. Our analyzes show that advection-dominated accretion disks are weakly unstable against local perturbations, if turbulent heat conduction is negligible.3)Turbulence in non-magnetized Keplerian disksKeplerian disks are highly stable against axially symmetric perturbations (Rayleigh criterion). In this sense, it is usually supposed that magnetic field will be necessary to make the disks turbulent (Balbus-Hawley instability). We think this argument is not always correct, and constructed a possible model of hydrodynamic turbulence in Keplerian disks.