标题： 相对论性喷流的传播和稳定性 显示英文标题

标题： Propagation and stability of relativistic jets

摘要： 简单观察高能稳态宇宙，可以明显看出与围绕致密天体（风和喷流）产生的外流有相关性。 对于相对论性喷流，人们认为它们是由克尔黑洞（布兰福德-扎涅克模型）或吸积盘（布兰福德-佩恩模型）提取旋转能量导致的。 吸积和/或黑洞旋转能量提供的大量能量预算中有一部分被用于喷流形成。 形成后，这些外流的加速和聚焦使它们能够传播到远离致密天体的大距离。 同步辐射冷却时间要求沿喷流重新加速粒子，以解释从千帕秒尺度观测到的高能和甚高能辐射。 在这些尺度上，射电星系中的喷流分为两种主要的形态/亮度类型，即Fanaroff-Riley I型和II型（FRI, FRII），后者比前者更亮、更集中且边缘更明亮，显示出明显的解束和减速迹象。 本文总结了一组可能有助于耗散磁场和动能的机制：磁流体力学不稳定性或喷流与障碍物的相互作用引发冲击波、剪切和混合，这些都是粒子加速的合理场景。 我还推导了一个表达式，用于计算恒星风开始显著掺混的距离，该表达式适用于FRI喷流。 最后，我讨论了河外和微类星体喷流中演化情景和主要耗散机制的差异。 显示英文摘要

摘要： A simple look at the steady high-energy Universe reveals a clear correlation with outflows generated around compact objects (winds and jets). In the case of relativistic jets, they are thought to be produced as a consequence of the extraction of rotational energy from a Kerr black hole (Blandford-Znajek), or from the disc (Blandford-Payne). A fraction of the large energy budget provided by accretion and/or black hole rotational energy is invested into jet formation. After formation, the acceleration and collimation of these outflows allow them to propagate to large distances away from the compact object. The synchrotron cooling times demand that re-acceleration of particles takes place along the jets to explain high-energy and very-high-energy emission from kiloparsec scales. At these scales, jets in radio galaxies are divided in two main morphological/luminosity types, namely, Fanaroff-Riley type I and II (FRI, FRII), the latter being more luminous, collimated and edge-brightened than the former, which show clear hints of decollimation and deceleration. In this contribution, I summarise a set of mechanisms that may contribute to dissipate magnetic and kinetic energy: Magnetohydrodynamic instabilities or jet-obstacle interactions trigger shocks, shearing and mixing, which are plausible scenarios for particle acceleration. I also derive an expression for the expected distance in which the entrainment by stellar winds starts to be relevant, which is applicable to FRI jets. Finally, I discuss the differences in the evolutionary scenarios and the main dissipative mechanisms that take place in extragalactic and microquasar jets.