Spontaneous Formation of Outflows Powered by Rotating Magnetized Accretion Flows in a Galactic Center
Spontaneous Formation of Outflows Powered by Rotating Magnetized Accretion Flows in a Galactic Center
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DOI：
10.3847/1538-4357/ac38a8
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
S. Takasao;Yuriko Shuto;K. Wada
中科院分区：
文献类型：
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作者：
S. Takasao;Yuriko Shuto;K. Wada
我们研究如何磁驱动外流供电的旋转，弱磁化吸积流到一个超大质量黑洞使用轴对称磁流体动力学模拟。我们提出的模型侧重于在史瓦西半径和银河系尺度之间的中间尺度上的吸积动力学，这是100 -100 pc。我们证明了在秒差距尺度上形成的旋转盘通过吸积获得极向磁场，这在某个点产生不对称的双极流出。外流的形成被发现遵循磁盘表面（磁泡）周围的强磁化区域的增长。双极流出在膨胀的气泡内持续增长。我们从理论上推导出我们的模型对应的流出增长的必要条件的磁泡的增长条件。我们发现双极外流的南北不对称结构起源于吸积流在盘外缘激发的复杂运动。双极流出包括多个微型流出和下行（失败流出）。微型外流来自磁集中（磁补丁）。磁块表现出向内漂移的运动，从而使流出不稳定。我们证明，向内漂移可以使用一个简单的磁补丁模型，考虑磁角动量提取建模。这项研究可能有助于理解如何在超大质量黑洞周围产生具有复杂子结构的非对称和非稳态流出，而无需来自吸积盘的强辐射或无线电喷流的夹带，例如无线电安静活动星系核中的分子流出，例如，NGC 1377
We investigate how magnetically driven outflows are powered by a rotating, weakly magnetized accretion flow onto a supermassive black hole using axisymmetric magnetohydrodynamic simulations. Our proposed model focuses on the accretion dynamics on an intermediate scale between the Schwarzschild radius and the galactic scale, which is ∼1–100 pc. We demonstrate that a rotating disk formed on a parsec-scale acquires poloidal magnetic fields via accretion, and this produces an asymmetric bipolar outflow at some point. The formation of the outflow was found to follow the growth of strongly magnetized regions around disk surfaces (magnetic bubbles). The bipolar outflow grew continuously inside the expanding bubbles. We theoretically derived the growth condition of the magnetic bubbles for our model that corresponds to a necessary condition for outflow growth. We found that the north–south asymmetrical structure of the bipolar outflow originates from the complex motions excited by accreting flows around the outer edge of the disk. The bipolar outflow comprises multiple mini-outflows and downflows (failed outflows). The mini-outflows emanate from the magnetic concentrations (magnetic patches). The magnetic patches exhibit inward drifting motions, thereby making the outflows unsteady. We demonstrate that the inward drift can be modeled using a simple magnetic patch model that considers magnetic angular momentum extraction. This study could be helpful for understanding how asymmetric and nonsteady outflows with complex substructures are produced around supermassive black holes without the help of strong radiation from accretion disks or entrainment by radio jets such as molecular outflows in radio-quiet active galactic nuclei, e.g., NGC 1377.