发表机构
Bar Ilan University（巴伊兰大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出辐射场非守恒性可快速独立产生并放大吸积流磁场，作为MRI的替代或补充机制，在广泛光度天体系统中适用。
AI 中文摘要
大尺度磁场在塑造吸积盘内部区域的动力学和结构以及黑洞和中子星附近产生的喷流中起着至关重要的作用。目前，被认为在吸积盘中产生和放大磁场的主要机制是磁旋转不稳定性（MRI）。在这里，我们表明非守恒的辐射场为吸积流中磁场的产生和放大提供了一种快速且独立的机制。一个明亮、致密的日冕产生一个辐射驱动的极向场，该场随后被较差自转放大，产生二次方的磁场增长，并且在广泛的日冕光度和尺寸以及MRI放大位置范围内，磁化时间尺度与MRI相当或更短。因此，该机制不仅提供了MRI的替代方案，而且提供了一个额外的、在参数空间的很大区域内占主导地位的磁场产生通道，可从零磁场的初始条件出发。由于辐射驱动的源直接源于辐射场的非守恒性质，这种磁场产生是黑洞吸积流中足够强且各向异性的辐射源的必然结果。更一般地，该机制仅需要非守恒的辐射场和等离子体的较差运动，因此预计将在广泛的光度天体物理系统中运行，包括活动星系核、伽马射线暴和潮汐瓦解事件。
英文摘要
Large scale magnetic fields play a crucial role in shaping the dynamics and structure of the inner parts of accretion disks and the resulting jets from the vicinity of black holes and neutron stars. Currently, the primary mechanism considered for generating and amplifying large scale magnetic fields in accretion disks is the magneto-rotational instability (MRI). Here we show that non-conservative radiation fields provide a rapid and independent mechanism for generating and amplifying magnetic fields in accretion flows. A luminous, compact corona generates a radiation-driven poloidal field that is subsequently amplified by differential rotation, yielding quadratic magnetic-field growth and, over a broad range of coronal luminosities and sizes and MRI amplification locations, magnetization on timescales comparable to or shorter than those of the MRI. The mechanism therefore provides not merely an alternative to MRI, but an additional and, over a substantial region of parameter space, dominant channel for magnetic-field generation from initial conditions with zero magnetic field. Since the radiation-driven source arises directly from the non-conservative nature of the radiation field, such magnetic-field generation is an inevitable consequence of sufficiently strong and anisotropic radiation sources in black-hole accretion flows. More generally, the mechanism requires only a non-conservative radiation field and differential plasma motion, and is therefore expected to operate in a broad range of luminous astrophysical systems, including active galactic nuclei, gamma-ray bursts, and tidal disruption events.
CommentsSubmitted to Physical Review Letters
