磁化宇宙网中的Shock waves：磁化率和cosmic-ray加速度的作用
Shock waves in the magnetized cosmic web: the role of obliquity and cosmic-ray acceleration
摘要：
结构形成激波被认为是宇宙中最大的宇宙射线加速器。然而，关于它们在加速相对论性电子和质子方面的效率作为它们的磁化性质的函数，即它们的磁场强度和拓扑结构的函数，仍然知之甚少。在这项工作中，我们分析了均匀和自适应网格分辨率模拟的大尺度结构与磁流体动力学网格代码恩佐，研究不同的宇宙磁性的现实情况下的冲击韧性的依赖。我们发现，冲击倾角通常比随机三维矢量分布所预期的更垂直，并且由于局部剪切运动的作用，这种效应在细丝附近特别突出。通过将这些结果与最近的粒子模拟工作相结合，我们估计了星系团中宇宙射线质子的通量，并表明，如果只有准平行冲击加速质子，那么费米-LAT错过强子伽马射线发射的探测之谜在原则上可以解释。另一方面，由于大量的准垂直冲击，对于大多数宇宙网来说，宇宙射线电子的加速仍然是允许的。我们讨论了定量的差异分析模型的磁化宇宙结构，这变得更加显着，在低宇宙overdensities。
英文摘要：
Structure formation shocks are believed to be the largest accelerators of cosmic rays in the Universe. However, little is still known about their efficiency in accelerating relativistic electrons and protons as a function of their magnetization properties, i.e. of their magnetic field strength and topology. In this work, we analyzed both uniform and adaptive mesh resolution simulations of large-scale structures with the magnetohydrodynamical grid code Enzo, studying the dependence of shock obliquity with different realistic scenarios of cosmic magnetism. We found that shock obliquities are more often perpendicular than what would be expected from a random three-dimensional distribution of vectors, and that this effect is particularly prominent in the proximity of filaments, due to the action of local shear motions. By coupling these results to recent works from particle-in-cell simulations, we estimated the flux of cosmic-ray protons in galaxy clusters, and showed that in principle the riddle of the missed detection of hadronic gamma-ray emission by the Fermi-LAT can be explained if only quasi-parallel shocks accelerate protons. On the other hand, for most of the cosmic web the acceleration of cosmic-ray electrons is still allowed, due to the abundance of quasi-perpendicular shocks. We discuss quantitative differences between the analyzed models of magnetization of cosmic structures, which become more significant at low cosmic overdensities.
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