Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets. I. A Systematic Study
Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets. I. A Systematic Study
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DOI：
10.3847/1538-4357/abb1b0
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发表时间：
2020-08
期刊：
影响因子：
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通讯作者：
Haocheng Zhang;Xiaocan Li;D. Giannios;F. Guo;Yi‐Hsin Liu;L. Dong
中科院分区：
文献类型：
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作者：
Haocheng Zhang;Xiaocan Li;D. Giannios;F. Guo;Yi‐Hsin Liu;L. Dong
耀变体是从超大质量黑洞流出的相对论性磁化等离子体，指向非常接近我们的视线。它们的发射是非热主导的，并且在整个电磁波谱中高度可变。相对论性磁重联被认为是耀变体耀斑中粒子加速的驱动因素。虽然最近的粒子在细胞（PIC）模拟自洽地研究了磁重联和粒子加速的演变，所产生的辐射信号还没有系统地探讨。特别是直接反映磁场重联过程中强动力学演化特征的极化特征还没有被仔细研究。在本文中，我们提出了一个系统的研究所产生的辐射和极化签名的磁重联耀变体，结合PIC和偏振辐射传输模拟与各种物理参数的基础上。我们确定了一个更难时，更明亮的光谱演变的趋势。此外，在同步加速器光谱分量中，高频带（紫外线到X射线）往往比低频带（红外线到光学）更早地闪烁。最重要的是，极化信号随着频率的增加而变化。我们发现，时间极化的变化强烈依赖于引导场强度。具体来说，重联与一个显着的引导场分量导致一个非常高的偏振度，矛盾的典型blazar观测，而大的偏振角旋转是独特的签名几乎反平行的磁场线之间的磁重联。这些旋转至少为90°，并且可以延伸到>180°，并且它们可以在任一方向上。这些结果意味着，耀变体，已显示出大的偏振角旋转本质上有更多的接近反平行磁场形态。
Blazars are relativistic magnetized plasma outflows from supermassive black holes that point very close to our line of sight. Their emission is nonthermal-dominated and highly variable across the entire electromagnetic spectrum. Relativistic magnetic reconnection has been proposed as the driver of particle acceleration during blazar flares. While recent particle-in-cell (PIC) simulations have self-consistently studied the evolution of magnetic reconnection and particle acceleration therein, the resulting radiation signatures have not been systematically explored. In particular, the polarization signatures, which directly reflect the characteristic strongly dynamical evolution of magnetic field during reconnection, have not been carefully investigated. In this paper, we present a systematic study of radiation and polarization signatures arising from magnetic reconnection in blazars, based on combined PIC and polarized radiation transfer simulations with various physical parameters. We identify a harder-when-brighter trend in the spectral evolution. Moreover, higher-frequency bands (ultraviolet to X-ray) tend to flare earlier than lower-frequency bands (infrared to optical) in the synchrotron spectral component. Most importantly, polarization signatures appear more variable with higher frequencies. We find that the variation in temporal polarization depends strongly on the guide field strength. Specifically, reconnection with a significant guide field component leads to a very high polarization degree that contradicts typical blazar observations, while large polarization angle rotations are unique signatures of magnetic reconnection between nearly antiparallel magnetic field lines. These rotations are at least 90° and can extend to >180°, and they may be in either direction. These results imply that blazars that have shown large polarization angle rotations intrinsically have more nearly antiparallel magnetic field morphology.