运动计算网格上相对论火球的Rayleigh-Taylor不稳定性
Rayleigh-Taylor Instability in a Relativistic Fireball on a Moving Computational Grid
摘要：
数值计算了洛伦兹因子Γ = 10、30和100时相对论外流减速引起的瑞利-泰勒不稳定性的增长和饱和。不稳定性产生湍流，其尺度表现出对洛伦兹因子的强烈依赖性，因为只有角尺寸小于1/Γ的模式才能增长。我们开发了一个简单的诊断来测量湍流波动中的动能，并计算出在受不稳定性影响的区域中湍流动能与热能的比率为0.03。虽然我们的数值计算不包括磁场，我们认为，小规模的湍流发电机放大磁场几乎相同的分数，给出了一个比率的磁场热能的~ 0.01，在一个因素的两倍。这种不稳定性完全破坏了喷出物和被卷起来的环周暴流介质之间的接触不连续性。反向激波是稳定的，但受到瑞利-泰勒不稳定性的影响，它加强了反向激波，并将其推离正向激波。前向冲击波阵面不受不稳定性的影响，但在爆炸的两个冲击波阶段，瑞利-泰勒指可以穿透到冲击波后面的高能区域的10%。我们计算了爆炸的余辉辐射，发现由于它的洛伦兹因子减小以及激波前沿的密度和压力改变，在稍后的时间出现了反向激波辐射峰。这些计算是使用包括移动计算网格的新型数值技术进行的。移动网格是必不可少的，因为它保持接触不连续性，以高精度，可以很容易地演变与非常大的洛伦兹因子流。
英文摘要：
We numerically calculate the growth and saturation of the Rayleigh-Taylor instability caused by the deceleration of relativistic outflows with Lorentz factor Γ = 10, 30, and 100. The instability generates turbulence whose scale exhibits strong dependence on Lorentz factor, as only modes with angular size smaller than 1/Γ can grow. We develop a simple diagnostic to measure the kinetic energy in turbulent fluctuations, and calculate a ratio of turbulent kinetic energy to thermal energy of .03 in the region affected by the instability. Although our numerical calculation does not include magnetic fields, we argue that small scale turbulent dynamo amplifies magnetic fields to nearly this same fraction, giving a ratio of magnetic to thermal energy of ~ .01, to within a factor of two. The instability completely disrupts the contact discontinuity between the ejecta and the swept up circumburst medium. The reverse shock is stable, but is impacted by the Rayleigh-Taylor instability, which strengthens the reverse shock and pushes it away from the forward shock. The forward shock front is unaffected by the instability, but Rayleigh-Taylor fingers can penetrate of order 10% of the way into the energetic region behind the shock during the two-shock phase of the explosion. We calculate afterglow emission from the explosion and find the reverse shock emission peaks at a later time due to its reduced Lorentz factor and modified density and pressure at the shock front. These calculations are performed using a novel numerical technique that includes a moving computational grid. The moving grid is essential as it maintains contact discontinuities to high precision and can easily evolve flows with extremely large Lorentz factors.
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。
