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arXiv 2602.01097astro-ph.HEphysics.plasm-ph
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辐射驱动超等分磁化场在吸积盘和喷流中的起源

Radiation-Driven Origin of Super-Equipartition Magnetic Fields in Accretion Discs and Outflows

Bar Ilan University(巴伊兰大学)

Mukesh Kumar Vyas, Asaf Pe'er

AI总结:

本研究揭示了辐射驱动机制在黑洞吸积盘和喷流中生成强磁场的作用,通过自洽MHD方程模拟发现磁场在粘性时间尺度内达到等分水平,为解释天体物理中大规模磁场结构提供了新路径。

摘要:

磁化场在黑洞周围的吸积物理中扮演着核心角色,但其在吸积流中的物理起源仍然是一个开放问题。在本工作中,我们研究了由各向异性辐射场触发的磁化场的生成及其后续演化,这些研究是在具有紧凑旋转内等离子体层的黑洞吸积盘中进行的。我们通过广义磁场演化MHD方程自洽地演算磁场,包括对流、剪切驱动诱导和霍尔效应。辐射场作为主要的磁场生成器,而磁化等离子体中的方位旋转则提供了快速放大。我们发现辐射生成的磁场通过开普勒旋转高效地达到主导的环向成分,导致在10倍太阳质量黑洞及其吸积盘-等离子体层中,辐射发射出等同于埃德蒙顿单位的光度时,磁场强度约为10^8 G。这些磁场在粘性时间尺度内被达到,并达到或超过基于气体压力的局部等分估计。当包括垂直喷流时,放大后的磁场被输送到等离子体层,磁化盘喷射的风和喷流前体,其磁场强度相似。我们的结果表明,辐射不仅是吸积流的被动成分,而且为生成动态显著的磁场提供了稳健且不可避免的触发机制。我们的结果为吸积盘及其周围的大规模、结构化磁场的起源提供了物理基础的解释。这种机制为不依赖外部供给磁通量而磁化吸积盘及其喷流提供了一条路径,对X射线双星、活动星系核及其他如伽马射线暴(GRBs)等暂现源具有广泛的含义。

英文摘要:

Magnetic fields play a central role in accretion physics around black holes, yet their physical origin within accretion flows remains an open problem. In this work, we investigate the generation and subsequent evolution of magnetic fields triggered by anisotropic radiation fields in black hole accretion discs with compact rotating inner corona. We self-consistently evolve the magnetic field using the generalized field evolution MHD equation, including advection, shear-driven induction, and Hall effects. The radiation field acts as a primary field generator, while azimuthal rotation in the magnetized plasma provides rapid amplification. We find that radiation-generated fields efficiently reach a dominant toroidal component by Keplerian rotation, leading to magnetic field strengths of order $\sim 10^{8}\,\mathrm{G}$ in the vicinity of a 10 solar mass black hole and accretion disc-corona emitting at luminosity equivalent to the Eddington unit. These magnetic fields are achieved within viscous timescales and reach or exceed local equipartition estimates based on gas pressure. When vertical outflows are included, the amplified magnetic fields are advected into the corona, magnetizing disc-launched winds and jet precursors with field strengths of similar order. Our results demonstrate that radiation is not merely a passive component of accretion flows, but provides a robust and unavoidable trigger for the generation of dynamically significant magnetic fields. Our results provide a physically grounded explanation for the origin of large-scale, structured magnetic fields in and around accretion discs. This mechanism offers a pathway for magnetizing accretion discs and their outflows without invoking externally supplied magnetic flux, with broad implications for X-ray binaries, active galactic nuclei and other transients such as gamma-ray bursts (GRBs).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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