Synchrotron self-Compton radiation from magnetically dominated turbulent plasmas in relativistic jets
Synchrotron self-Compton radiation from magnetically dominated turbulent plasmas in relativistic jets
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DOI：
10.1093/mnras/stab1702
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发表时间：
2021-06
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影响因子：
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通讯作者：
E. Sobacchi;L. Sironi;A. Beloborodov
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作者：
E. Sobacchi;L. Sironi;A. Beloborodov
由旋转黑洞发射的相对论性喷流是非热辐射的强大发射器。通过电磁应力提取旋转能量产生磁主导的射流，这可能成为湍流。从第一性原理对磁主导等离子体湍流的研究表明，大多数加速粒子具有较小的俯仰角，即粒子速度几乎与局部磁场对齐。我们研究了各向异性粒子在快速冷却状态下的同步自康普顿辐射。小的俯仰角降低了同步加速器的冷却速率，促进了逆康普顿（IC）冷却的作用，这可能发生在两种不同的状态下。在汤姆逊区，同步加速器和集成电路元件都有软谱，νFν∝ν1/2。在Klein-Nishina体制中，同步辐射在很宽的频率范围内具有硬谱，通常为ν ν∝ν。我们的结果对BL - Lacs和伽马射线暴（GRBs）的建模具有启示意义。当Klein-Nishina效应较小时，BL lac产生软同步加速器和集成电路光谱。观测到的同步加速器和集成电路的光度具有典型的可比性，这表明在俯仰角θ & 0.1时具有中等的各向异性。当θ 0.1时可能会产生罕见的孤射线耀斑。当发射粒子在Klein-Nishina模式下进行IC冷却时，grb的硬光谱可能与同步辐射一致，正如所期望的那样，俯仰角为θ ~ 0.1。Blazar和GRB的光谱可以用具有相似电子等离子体磁化参数σe ~ 104的湍流射流来解释，对于电子-质子等离子体，其磁化参数σ = (me/mp)σe ~ 10。
Relativistic jets launched by rotating black holes are powerful emitters of non-thermal radiation. Extraction of the rotational energy via electromagnetic stresses produces magneticallydominated jets, which may become turbulent. Studies of magnetically-dominated plasma turbulence from first principles show that most of the accelerated particles have small pitch angles, i.e. the particle velocity is nearly aligned with the local magnetic field. We examine synchrotron-self-Compton radiation from anisotropic particles in the fast cooling regime. The small pitch angles reduce the synchrotron cooling rate and promote the role of inverse Compton (IC) cooling, which can occur in two different regimes. In the Thomson regime, both synchrotron and IC components have soft spectra, νFν ∝ ν1/2. In the Klein-Nishina regime, synchrotron radiation has a hard spectrum, typically νFν ∝ ν, over a broad range of frequencies. Our results have implications for the modelling of BL Lacs and Gamma-Ray Bursts (GRBs). BL Lacs produce soft synchrotron and IC spectra, as expected when Klein-Nishina effects are minor. The observed synchrotron and IC luminosities are typically comparable, which indicates a moderate anisotropy with pitch angles θ & 0.1. Rare orphan gamma-ray flares may be produced when θ 0.1. The hard spectra of GRBs may be consistent with synchrotron radiation when the emitting particles are IC cooling in the Klein-Nishina regime, as expected for pitch angles θ∼ 0.1. Blazar and GRB spectra can be explained by turbulent jets with a similar electron plasma magnetisation parameter, σe ∼ 104, which for electron-proton plasmas corresponds to an overall magnetisation σ = (me/mp)σe ∼ 10.