论文标题
喷嘴冲击,磁盘的撕裂和彩流器驱动3D GRMHD模拟的扭曲薄磁盘的快速积聚
Nozzle Shocks, Disk Tearing and Streamers Drive Rapid Accretion in 3D GRMHD Simulations of Warped Thin Disks
论文作者
论文摘要
相对于BH旋转,通常会将馈入黑洞(BH)的气体动量错过,从而导致倾斜的吸积盘。 BH的旋转拖延了周围的时空,表现为透明的扭矩,导致磁盘进动和翘曲。我们通过模拟薄($ h/r = 0.02 $),高度倾斜($ \ \ \ \ \ \ \ \ \ circ $)的积聚盘来研究这些过程,我们在极高的分辨率上($ a = 0.9375 $)BH围绕($ a = 0.9375 $)BH,我们在极高的分辨率上使用了一般性的巨大脑料(GRMANTODRADY HYDRADRODYRADYSIC)(GRMANT)(GRMAND)执行。磁盘会显着扭曲,并连续撕裂成两个单独的进攻子盘。我们发现,质量积聚率远远超过了标准的$α$ viscosity预期。我们确定了扭曲磁盘特异性的两种新型耗散机制,这些磁盘是积聚的主要驱动因素,与通常认为会驱动积聚的局部湍流应力不同。特别是,我们确定了在整个磁盘中发生的两倍的极端尺度高度振荡。当尺度高度压缩时,“喷嘴”冲击形成,消散轨道能量并驱动积聚。与这种现象分开,在撕裂的位置也存在极端的耗散。这导致形成了低角动量“流媒体”,将下雨降到内部的子盘上,使它震惊。在内部二盘中添加低角度动量气体也会导致其快速增生,即使它与BH旋转瞬时对齐并因此不破坏。这些机制(如果一般)显着修改了标准积聚范例。此外,它们可能会驱动比$α$ disks中预期的时间尺寸要短的时间表的结构变化,这可能解释了活跃银河系核中观察到的一些极端变异性。
The angular momentum of gas feeding a black hole (BH) is typically misaligned with respect to the BH spin, resulting in a tilted accretion disk. Rotation of the BH drags the surrounding space-time, manifesting as Lense-Thirring torques that lead to disk precession and warping. We study these processes by simulating a thin ($H/r=0.02$), highly tilted ($\mathcal{T}=65^\circ$) accretion disk around a rapidly rotating ($a=0.9375$) BH at extremely high resolutions, which we performed using the general-relativistic magnetohydrodynamic (GRMHD) code H-AMR. The disk becomes significantly warped and continuously tears into two individually precessing sub-disks. We find that mass accretion rates far exceed the standard $α$-viscosity expectations. We identify two novel dissipation mechanisms specific to warped disks that are the main drivers of accretion, distinct from the local turbulent stresses that are usually thought to drive accretion. In particular, we identify extreme scale height oscillations that occur twice an orbit throughout our disk. When the scale height compresses, `nozzle' shocks form, dissipating orbital energy and driving accretion. Separate from this phenomenon, there is also extreme dissipation at the location of the tear. This leads to the formation of low-angular momentum `streamers' that rain down onto the inner sub-disk, shocking it. The addition of low angular momentum gas to the inner sub-disk causes it to rapidly accrete, even when it is transiently aligned with the BH spin and thus unwarped. These mechanisms, if general, significantly modify the standard accretion paradigm. Additionally, they may drive structural changes on much shorter timescales than expected in $α$-disks, potentially explaining some of the extreme variability observed in active galactic nuclei.