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arXiv 0804.0052astro-ph
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非磁化电子-离子等离子体中的非相对论无碰撞激波

Non-relativistic Collisionless Shocks in Unmagnetized Electron-Ion Plasmas

Tsunehiko N. Kato, Hideaki Takabe

摘要:

通过二维粒子模拟,我们证明了在非磁化电子-离子等离子体中,韦伯介导的无碰撞激波是以非相对论传播速度(0.1c < V < 0.45c)驱动的。结果表明,激波过渡区附近的数密度和平均速度的分布,用各自的上游值归一化,几乎与上游体积速度无关,即,冲击波的速度特别是,冲击过渡区的宽度是~100离子惯性长度的冲击速度无关。对于这些激波,激波过渡区内由韦伯型不稳定性产生的磁场的能量密度通常达到上游体动能能量密度的1-2%。这种机制可能解释了无碰撞冲击的强大形成,例如,由年轻的超新星遗迹驱动,没有假设宇宙中存在外部磁场。

英文摘要:

We show that the Weibel-mediated collisionless shocks are driven at non-relativistic propagation speed (0.1c < V < 0.45c) in unmagnetized electron-ion plasmas by performing two-dimensional particle-in-cell simulations. It is shown that the profiles of the number density and the mean velocity in the vicinity of the shock transition region, which are normalized by the respective upstream values, are almost independent of the upstream bulk velocity, i.e., the shock velocity. In particular, the width of the shock transition region is ~100 ion inertial length independent of the shock velocity. For these shocks the energy density of the magnetic field generated by the Weibel-type instability within the shock transition region reaches typically 1-2% of the upstream bulk kinetic energy density. This mechanism probably explains the robust formation of collisionless shocks, for example, driven by young supernova remnants, with no assumption of external magnetic field in the universe.

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