Spinning black holes magnetically connected to a Keplerian disk: Magnetosphere, reconnection sheet, particle acceleration, and coronal heating
Spinning black holes magnetically connected to a Keplerian disk: Magnetosphere, reconnection sheet, particle acceleration, and coronal heating
复制标题
与开普勒盘磁性连接的旋转黑洞：磁层、重联片、粒子加速和日冕加热
DOI：
10.1051/0004-6361/202142847
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发表时间：
2022
影响因子：
6.5
通讯作者：
Parfrey, K.
中科院分区：
文献类型：
--
作者：
El Mellah, I.;Cerutti, B.;Crinquand, B.;Parfrey, K.
背景吸积黑洞（BH）可能被高度磁化的等离子体包围，该等离子体由有组织的极向磁场穿过。高能非热耀斑和幂律光谱分量可能源自热、无碰撞且几乎无力的日冕。我们经常从这些系统中观察到的喷流被认为是由旋转驱动和磁力驱动的。 目的我们研究轴对称的 BH 磁层，其中固定在周围圆盘中的一小部分磁场线连接到旋转 BH 的事件视界。对于不同的 BH 自旋，我们确定了 30 个引力半径内磁重联的条件和位置。方法利用完全通用的相对论细胞内粒子代码 GRZeltron，我们求解了电子-正电子对等离子体和 BH 周围电磁场的时间相关动力学。对齐的圆盘由开普勒旋转中稳定且完美传导的等离子体表示，由偶极磁场穿过。结果对于克尔 BH 周围的顺行圆盘，磁层拓扑是混合的。穿过地平线的扭曲开放磁力线为布兰福德-兹纳耶克喷气式飞机提供动力，而其足点超出盘上临界距离的开放磁力线可以发射磁力离心风。在最里面的区域，耦合磁场线确保了 BH 和磁盘之间大量角动量和能量的传递。从这三个区域交叉点的 Y 点开始，形成电流片，通过磁重联产生生动的粒子加速。我们计算当前片状发射的同步加速器图像。结论我们对射流功率和 BH-圆盘交换的估计与从纯无力模型得出的估计相匹配。粒子在 Y 点加速，该点充当所谓电晕的热源。它为反射模型提供了磁盘上方物理激励的环形硬 X 射线源。阵发性等离子喷射或许可以解释天鹅座 X-1 在高软状态下观察到的毫秒耀斑，但速度太快，无法解释人马座 A* 每天的非热耀斑。从 Y 点向下流向圆盘的粒子可能会在最外层闭合磁场线的足点产生热点。
ContextAccreting black holes (BHs) may be surrounded by a highly magnetized plasma threaded by an organized poloidal magnetic field. Nonthermal flares and power-law spectral components at high energy could originate from a hot, collisionless, and nearly force-free corona. The jets we often observe from these systems are believed to be rotation-powered and magnetically driven.AimsWe study axisymmetric BH magnetospheres, where a fraction of the magnetic field lines anchored in a surrounding disk are connected to the event horizon of a rotating BH. For different BH spins, we identify the conditions and sites of magnetic reconnection within 30 gravitational radii.MethodsWith the fully general relativistic particle-in-cell code GRZeltron, we solve the time-dependent dynamics of the electron–positron pair plasma and of the electromagnetic fields around the BH. The aligned disk is represented by a steady and perfectly conducting plasma in Keplerian rotation, threaded by a dipolar magnetic field.ResultsFor prograde disks around Kerr BHs, the topology of the magnetosphere is hybrid. Twisted open magnetic field lines crossing the horizon power a Blandford-Znajek jet, while open field lines with their footpoint beyond a critical distance on the disk could launch a magneto-centrifugal wind. In the innermost regions, coupling magnetic field lines ensure the transfer of significant amounts of angular momentum and energy between the BH and the disk. From the Y point at the intersection of these three regions, a current sheet forms where vivid particle acceleration via magnetic reconnection takes place. We compute the synchrotron images of the current sheet emission.ConclusionsOur estimates for jet power and BH–disk exchanges match those derived from purely force-free models. Particles are accelerated at the Y point, which acts as a heat source for the so-called corona. It provides a physically motivated ring-shaped source of hard X-rays above the disk for reflection models. Episodic plasmoid ejection might explain millisecond flares observed in Cygnus X-1 in the high-soft state, but are too fast to account for daily nonthermal flares from Sgr A*. Particles flowing from the Y point down to the disk could produce a hot spot at the footpoint of the outermost closed magnetic field line.