论文标题
黑洞积聚磁盘中的磁重新连接和热点形成
Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks
论文作者
论文摘要
由于电流板上的磁重新连接而形成的热点或浆液物被猜测可频繁地X射线和近红外耀斑，Sgr a*（我们星系中心的黑洞）。目前尚不清楚在黑洞积聚磁盘中如何，何时和何时形成当前床单。我们在一系列积聚流中执行轴对称的一般偏见的电阻性磁流失动力学模拟，以模拟重新连接和浆液形成。电流片和浆液是无处不在的特征，无论磁盘中的初始磁场，积聚的稳态阶段的磁化以及黑洞的旋转。在事件范围内的10个Schwarzschild Radii中，我们观察到形成的浆体形成，之后它们可以合并，生长到几个Schwarzschild Radii的宏观尺度上，并最终沿着喷气机的鞘或磁盘延伸。大型浆液可通过重新连接为相对论温度，并有助于射流的肢体吹捧。我们发现，只有在磁性捕集的磁盘中形成的热点才能解释SGR A*耀斑的能量。耀斑周期由重新连接率确定，在所有情况下，我们认为在0.01c和0.03c之间，这与孤立的Harris型电流电流板的重新连接研究一致。我们量化磁耗散和非理想的电场，这些电场可以有效地注入非热颗粒。我们表明，显式电阻率允许收敛的数值溶液，因此，电磁能的演化和耗散与此处考虑的极端分辨率独立于网格尺度。
Hot spots, or plasmoids, forming due to magnetic reconnection in current sheets, are conjectured to power frequent X-ray and near-infrared flares from Sgr A*, the black hole in the center of our Galaxy. It is unclear how, where, and when current sheets form in black-hole accretion disks. We perform axisymmetric general-relativistic resistive magnetohydrodynamics simulations to model reconnection and plasmoid formation in a range of accretion flows. Current sheets and plasmoids are ubiquitous features which form regardless of the initial magnetic field in the disk, the magnetization in the quasi-steady-state phase of accretion, and the spin of the black hole. Within 10 Schwarzschild radii from the event horizon, we observe plasmoids forming, after which they can merge, grow to macroscopic scales of the order of a few Schwarzschild radii, and are ultimately advected along the jet's sheath or into the disk. Large plasmoids are energized to relativistic temperatures via reconnection and contribute to the jet's limb-brightening. We find that only hot spots forming in magnetically arrested disks can potentially explain the energetics of Sgr A* flares. The flare period is determined by the reconnection rate, which we find to be between 0.01c and 0.03c in all cases, consistent with studies of reconnection in isolated Harris-type current sheets. We quantify magnetic dissipation and non-ideal electric fields which can efficiently inject non-thermal particles. We show that explicit resistivity allows for converged numerical solutions, such that the electromagnetic energy evolution and dissipation become independent of the grid scale for the extreme resolutions considered here.
