arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1201.3469astro-ph.HEastro-ph.CO
收藏

磁主导脉冲流中的激波耗散

Shock Dissipation in Magnetically Dominated Impulsive Flows

S. S. Komissarov

摘要:

我们已经重新讨论了冲击耗散和发射的问题及其影响的内部冲击模型的提示伽玛暴发射和研究它的上下文中的脉冲坡印廷占主导地位的流量。我们的结果表明,除非伽玛暴喷流的磁化强度非常高,在瞬发区σ> 100,否则磁模型仍可能与观测结果相一致。耗散效率降低的主要影响仅仅是耗散区尺寸的增加,即使对于高度磁化的伽玛暴射流,这个尺寸也可能保持在外部激波半径以下,只要中央发动机能够在时间尺度上发射磁壳,其时间尺度远低于典型的观察到的一秒的变化尺度。我们的分析和数值计算结果表明,磁壳开始强烈相互作用,以及之前,他们达到滑行半径。因此,在耗散区中的脉冲射流最好描述为不是壳的集合,而是具有高振幅磁声波分量的连续高磁化流。耗散的波能如何在辐射和径向喷流的整体动能之间精确地分配取决于辐射冷却和绝热冷却的相对速率。在快速辐射冷却状态下,相应的辐射效率可以与波对其能量预算的贡献一样高,而与磁化无关。此外,在离开瞬发区后,喷流可能仍然保持坡印廷主导,导致反向激波的发射比非磁性模型更弱。

英文摘要:

We have revisited the issue of shock dissipation and emission and its implications for the internal shock model of the prompt GRB emission and studied it in the context of impulsive Poynting-dominated flows. Our results show that unless the magnetization of GRB jets is extremely high, σ> 100 in the prompt emission zone, the magnetic model may still be compatible with the observations. The main effect of reduced dissipation efficiency is merely an increase in the size of the dissipation zone and even for highly magnetised GRB jets this size may remain below the external shock radius, provided the central engine can emit magnetic shells on the time scale well below the typical observed variability scale of one second. Our analytical and numerical results suggest that magnetic shells begin strongly interact with each other well before they reach the coasting radius. As the result, the impulsive jet in the dissipation zone is best described not as a collection of shells but as a continuous highly magnetised flow with a high amplitude magnetosonic wave component. How exactly the dissipated wave energy is distributed between the radiation and the bulk kinetic energy of radial jets depends on the relative rates of radiative and adiabatic cooling. In the fast radiative cooling regime, the corresponding radiative efficiency can be as high as the wave contribution to their energy budget, independently of the magnetization. Moreover, after leaving the zone of prompt emission the jet may still remain Poynting-dominated, leading to weaker emission from the reverse shock compared to non-magnetic models.

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。

↑