标题： 相对论性激波中的粒子加速 显示英文标题

标题： Particle acceleration at relativistic shock waves

摘要： 相对论性源，例如伽马射线暴、脉冲星风星云和强大的活动星系核产生相对论性喷流，导致形成无碰撞激波，粒子加速被认为是在这里发生的。 在过去十年中，由于分析研究和高水平数值模拟的结合，我们对相对论性激波加速的理解得到了改善。 在超相对论性激波中，受激波等离子体的普遍横向磁场和大对流速度的影响，粒子加速变得困难。 因此，需要快速增长的微观湍流使费米过程发挥作用。 人们认为，数值模拟也支持这一观点，即超热粒子进入激波前缘会产生磁湍流，而这种湍流反过来会产生通过费米机制进行粒子加速所需的散射过程。 通过比较激波前缘中微不稳定性的发展时间尺度和前缘穿越时间尺度，可以确定在磁化率和激波洛伦兹因子方面可能激发微观湍流的区域，从而判断费米加速是否被触发以及如何被触发。 这些发现在此总结，并得出天体物理后果。 显示英文摘要

摘要： Relativistic sources, e.g. gamma-ray bursts, pulsar wind nebulae and powerful active galactic nuclei produce relativistic outflows that lead to the formation of collisionless shock waves, where particle acceleration is thought to take place. Our understanding of relativistic shock acceleration has improved in the past decade, thanks to the combination of analytical studies and high level numerical simulations. In ultra-relativistic shocks, particle acceleration is made difficult by the generically transverse magnetic field and large advection speed of the shocked plasma. Fast growing microturbulence is thus needed to make the Fermi process operative. It is thought, and numerical simulations support that view, that the penetration of supra-thermal particles in the shock precursor generates a magnetic turbulence which in turn produces the scattering process needed for particle acceleration through the Fermi mechanism. Through the comparison of the growth timescale of the microinstabilities in the shock precursor and the precursor crossing timescale, it is possible to delimit in terms of magnetization and shock Lorentz factor the region in which micro-turbulence may be excited, hence whether and how Fermi acceleration is triggered. These findings are summarized here and astrophysical consequences are drawn.