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arXiv 2003.00927astro-ph.HE
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电子的同步辐射在云团环境中向甚高能量的扩展

Extension of the synchrotron radiation of electrons to very high energies in clumpy environments

Dmitry Khangulyan, Felix Aharonian, Carlo Romoli, Andrew Taylor

摘要:

相对论电子的同步辐射冷却是天体物理中最有效的辐射机制之一。它不仅伴随着粒子的加速过程,而且对母电子能量分布的形成有反馈作用。电子的辐射冷却时间随着能量的增加而减少,如$t_{\rm syn} \propto 1/E$;相应地,总辐射效率随着能量的增加而增加。另一方面,这种效应严格限制了单个光子的最大能量。即使在所谓的极端加速器中,加速以理想磁流体等离子体所允许的最高速率$t_{\rm acc}^{-1} = eBc/E$进行,同步辐射也不能远远超出由电子质量和精细结构常数决定的特征能量:$h ν^{\rm max} \sim m_e c^2/α\sim 70 \rm\,MeV$。在本文中,我们提出了一个模型,其中同步辐射的形成发生在位于粒子加速器内部的紧凑磁滴中,并建立了计算此类系统产生的同步辐射的形式。我们证明,对于某些组合的参数特征的加速器和磁斑点,同步辐射可以扩展到超过这个限制的几个数量级。这种情况需要粒子加速器的弱磁化,以及气体内能在足够小的斑点中有效地转换成磁能。所需的斑点的尺寸受到磁镜效应的约束,磁镜效应可以在一定条件下防止颗粒穿透到强磁场区域中。

英文摘要:

The synchrotron cooling of relativistic electrons is one of the most effective radiation mechanisms in astrophysics. It not only accompanies the process of particle acceleration but also has feedback on the formation of the energy distribution of the parent electrons. The radiative cooling time of electrons decreases with energy as $t_{\rm syn} \propto 1/E$; correspondingly the overall radiation efficiency increases with energy. On the other hand, this effect strictly limits the maximum energy of individual photons. Even in the so-called extreme accelerators, where the acceleration proceeds at the highest possible rate, $t_{\rm acc}^{-1} = eBc/E$, allowed in an ideal magnetohydrodynamic plasma, the synchrotron radiation cannot extend well beyond the characteristic energy determined by the electron mass and the fine-structure constant: $h ν^{\rm max} \sim m_e c^2/α\sim 70 \rm\,MeV$. In this paper, we propose a model in which the formation of synchrotron radiation takes place in compact magnetic blobs located inside the particle accelerator and develop a formalism for calculations of synchrotron radiation emerging from such systems. We demonstrate that for certain combinations of parameters characterizing the accelerator and the magnetic blobs, the synchrotron radiation can extend beyond this limit by a several orders of magnitude. This scenario requires a weak magnetization of the particle accelerator, and an efficient conversion of gas internal energy into magnetic energy in sufficiently small blobs. The required size of the blobs is constrained by the magnetic mirroring effect, that can prevent particle penetration into the regions of strong magnetic field under certain conditions.

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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