Galaxy clusters grow by gas accretion, mostly from mergers of substructures, which release powerful shock waves into cosmic plasmas and convert a fraction of kinetic energy into thermal energy, amplification of magnetic fields and into the acceleration of energetic particles. The modeling of the radio signature of cosmic shocks, combined with the lack of detected γ$\gamma $-rays from cosmic ray (CR) protons, poses challenges to our understanding of how cosmic rays get accelerated and stored in the intracluster medium. Here we review the injection of CRs by cosmic shocks of different strengths, combining the detailed “microscopic” view of collisionless processes governing the creation of non-thermal distributions of electrons and protons in cluster shocks (based on analytic theory and particle-in-cell simulations), with the “macroscopic” view of the large-scale distribution of cosmic rays, suggested by modern cosmological simulations. Time dependent non-linear kinetic models of particle acceleration by multiple internal shocks with large scale compressible motions of plasma with soft CR spectra containing a noticeable energy density in the super-thermal protons of energies below a few GeV which is difficult to constrain by Fermi observations are discussed. We consider the effect of plasma composition on CR injection and super-thermal particle population in the hot intracluster matter which can be constrained by fine high resolution X-ray spectroscopy of Fe ions.

中文翻译：

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星系团中的冲击和非热粒子

星系团通过气体吸积而增长，主要来自子结构的合并，这些子结构将强大的冲击波释放到宇宙等离子体中，并将​​一小部分动能转化为热能、磁场放大和高能粒子的加速。宇宙冲击的无线电特征的建模，加上缺乏检测到的来自宇宙射线 (CR) 质子的 γ$\gamma $ 射线，对我们理解宇宙射线如何加速并存储在簇内介质中提出了挑战。在这里，我们回顾了不同强度的宇宙冲击对 CR 的注入，结合无碰撞过程的详细“微观”观点，控制簇冲击中电子和质子的非热分布的产生（基于解析理论和细胞内粒子）模拟），现代宇宙学模拟提出的宇宙射线大规模分布的“宏观”观点。粒子加速的时间相关非线性动力学模型由多个内部冲击与等离子体的大规模可压缩运动与软 CR 谱包含显着的能量密度低于几个 GeV 的能量的超热质子，这是难以约束的费米观测进行了讨论。我们考虑了等离子体成分对 CR 注入和热簇内物质中超热粒子数量的影响，这可以通过 Fe 离子的精细高分辨率 X 射线光谱进行限制。粒子加速的时间相关非线性动力学模型由多个内部冲击与等离子体的大规模可压缩运动与软 CR 谱包含显着的能量密度低于几个 GeV 的能量的超热质子，这是难以约束的费米观测进行了讨论。我们考虑了等离子体成分对 CR 注入和热簇内物质中超热粒子数量的影响，这可以通过 Fe 离子的精细高分辨率 X 射线光谱进行限制。粒子加速的时间相关非线性动力学模型由多个内部冲击与等离子体的大规模可压缩运动与软 CR 谱包含显着的能量密度低于几个 GeV 的能量的超热质子，这是难以约束的费米观测进行了讨论。我们考虑了等离子体成分对 CR 注入和热簇内物质中超热粒子数量的影响，这可以通过 Fe 离子的精细高分辨率 X 射线光谱进行限制。