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arXiv 1305.4656astro-ph.HE
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年轻超新星遗迹中径向排列磁场的起源

Origin of Radially Aligned Magnetic Fields in Young Supernova Remnants

Tsuyoshi Inoue, Jiro Shimoda, Yutaka Ohira, Ryo Yamazaki

摘要:

偏振同步辐射的射电观测表明,在一些年轻的超新星遗迹中,下游的磁场是径向的。本文利用三维磁流体动力学模拟方法研究了由Richtmyer-Meshkov不稳定性驱动的湍流超新星遗迹的磁场分布,即脉动激波的影响。我们发现,诱导的湍流具有径向偏置的各向异性的速度色散,导致选择性放大的径向分量的磁场。激波与上游密度涨落的相互作用导致了Richtmyer-Meshkov不稳定性。未来的高分辨率偏振观测可以区分以下几种可能的上游密度波动:(i)由ISM中所谓的大幂律天空中的大尺度湍流级联引起的不均匀性,(ii)由宇宙线修正激波中的德鲁里不稳定性产生的结构,以及(iii)由宇宙线流动不稳定性的非线性反馈引起的波动。

英文摘要:

It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic field in some young supernova remnants are oriented radially. We study magnetic field distribution of turbulent supernova remnant driven by the Richtmyer-Meshkov instability -- in other words, the effect of rippled shock -- by using three-dimensional magnetohydrodynamics simulations. We find that the induced turbulence has radially biased anisotropic velocity dispersion that leads to a selective amplification of the radial component of the magnetic field. The Richtmyer-Meshkov instability is induced by the interaction between the shock and upstream density fluctuations. Future high-resolution polarization observations can distinguish the following candidates responsible for the upstream density fluctuations: (i) inhomogeneity caused by the cascade of large-scale turbulence in the ISM so-called the big-power-law-in-the-sky, (ii) structures generated by the Drury instability in the cosmic-ray modified shock, and (iii) fluctuations induced by the non-linear feedback of the cosmic-ray streaming instability.

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