标题： 相对论磁化碰撞less电子-离子激波中的粒子加速 显示英文标题

标题： Particle Acceleration in Relativistic Magnetized Collisionless Electron-Ion Shocks

摘要： 我们通过二维半粒子模拟研究了相对论磁化无碰撞电子-离子冲击中的冲击结构和粒子加速机制，离子与电子的质量比 (m_i/m_e) 范围从16到1000。 我们探索了预冲击磁场与冲击法线之间的一系列倾角。 在“次光速”冲击中，相对论粒子可以沿磁场线逃离冲击前方，离子通过一种类似Fermi机制被有效加速。 下游离子谱由相对论麦克斯韦分布和高能幂律尾组成，其中约5%的离子和约30%的离子能量位于幂律尾中。 其斜率为-2.1。 上游电子的能量低于离子，因此它们更强烈地受磁场影响。 因此，在被拖拽到下游之前，只有约1%的入射电子在冲击处被Fermi加速，这些电子形成了一个陡峭的幂律尾（斜率-3.5）。 对于“超光速”冲击，由于相对论粒子无法沿着磁场线超越冲击波，自生成湍流不够强，无法允许有效的Fermi加速，因此下游离子和电子谱与热分布一致。 由于冲击波向上游发射出强烈的电磁波，入射电子被加热至与离子达到能量均分。 因此，相对论电子-离子冲击的高效电子加热（超过上游离子能量的15%）是普遍特征，但显著的非热电子加速（按数量计>2%，按能量计>10%，斜率比-2.5平缓）在磁化流中难以实现，需要弱磁化冲击（磁化度<1e-3）。 这些发现对涉及相对论磁化电子-离子冲击粒子加速的活动星系核喷流和伽马射线暴模型施加了重要的限制。 显示英文摘要

摘要： We investigate shock structure and particle acceleration in relativistic magnetized collisionless electron-ion shocks by means of 2.5D particle-in-cell simulations with ion-to-electron mass ratios (m_i/m_e) ranging from 16 to 1000. We explore a range of inclination angles between the pre-shock magnetic field and the shock normal. In "subluminal" shocks, where relativistic particles can escape ahead of the shock along the magnetic field lines, ions are efficiently accelerated via a Fermi-like mechanism. The downstream ion spectrum consists of a relativistic Maxwellian and a high-energy power-law tail, which contains ~5% of ions and ~30% of ion energy. Its slope is -2.1. Upstream electrons enter the shock with lower energy than ions, so they are more strongly tied to the field. As a result, only ~1% of the incoming electrons are Fermi-accelerated at the shock before being advected downstream, where they populate a steep power-law tail (with slope -3.5). For "superluminal" shocks, where relativistic particles cannot outrun the shock along the field, the self-generated turbulence is not strong enough to permit efficient Fermi acceleration, and the ion and electron downstream spectra are consistent with thermal distributions. The incoming electrons are heated up to equipartition with ions, due to strong electromagnetic waves emitted by the shock into the upstream. Thus, efficient electron heating (>15% of the upstream ion energy) is the universal property of relativistic electron-ion shocks, but significant nonthermal acceleration of electrons (>2% by number, >10% by energy, with slope flatter than -2.5) is hard to achieve in magnetized flows and requires weakly magnetized shocks (magnetization <1e-3). These findings place important constraints on the models of AGN jets and Gamma Ray Bursts that invoke particle acceleration in relativistic magnetized electron-ion shocks.