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arXiv 1204.5697astro-ph.HE
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相互作用的稀疏波对相对论热喷流的影响

Effect of Interacting Rarefaction Waves on Relativistically Hot Jets

Jin Matsumoto, Youhei Masada, Kazunari Shibata

摘要:

通过相对论流体动力学模拟,研究了稀薄加速对相对论热射流传播动力学和结构的影响。本文着重研究了圆柱射流与周围介质交界面上激发的稀疏波的非线性相互作用。从简化的一维模型与径向射流结构,我们发现,在相对论压力的减少,由于相互作用的稀疏波在射流的中心区域瞬时产生一个更强大的推动散装射流比预期从单一的稀疏加速。这导致热动能和体动能之间的循环原位能量转换,其引起射流的径向振荡运动。振荡时标的特征在于射流与周围介质的初始压力比,并且遵循简单的标度关系$τ_{\rm oscillation} \propto (P_{\rm jet,0}/P_{\rm amb,0})^{1/2}$。从扩展的二维模拟证实,在一维系统中的这种径向振荡运动表现为在一个更现实的情况下,相对论热射流传播通过周围介质的射流的结构的调制。研究发现,当周围介质为幂律压力分布时,调制结构$λ$中沿射流传播方向的约束区尺寸按照自相似关系$λ\propto t^{α/2}$演化,其中$α$为压力分布的幂律指数.

英文摘要:

The effect of rarefaction acceleration on the propagation dynamics and structure of relativistically hot jets is studied through relativistic hydrodynamic simulations. We emphasize the nonlinear interaction of rarefaction waves excited at the interface between a cylindrical jet and the surrounding medium. From simplified one-dimensional models with radial jet structure, we find that a decrease in the relativistic pressure due to the interacting rarefaction waves in the central zone of the jet transiently yields a more powerful boost of the bulk jet than that expected from single rarefaction acceleration. This leads to a cyclic in-situ energy conversion between thermal and bulk kinetic energies which induces radial oscillating motion of the jet. The oscillation timescale is characterized by the initial pressure ratio of the jet to the ambient medium, and follows a simple scaling relation $τ_{\rm oscillation} \propto (P_{\rm jet,0}/P_{\rm amb,0})^{1/2}$. It is confirmed from extended two-dimensional simulations that this radial oscillating motion in the one-dimensional system manifests as modulation of the structure of the jet in a more realistic situation where a relativistically hot jet propagates through an ambient medium. It is found that when the ambient medium has a power law pressure distribution, the size of the reconfinement region along the propagation direction of the jet in the modulation structure $λ$ evolves according to a self-similar relation $λ\propto t^{α/2}$ where $α$ is the power-law index of the pressure distribution.

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