Title: GeV-TeV cosmic-ray spectral anomaly as due to re-acceleration by weak shocks in the Galaxy Show Chinese title

Title: GeV-TeV宇宙射线能谱异常归因于银河系弱冲击的再加速

Abstract: Recent cosmic-ray measurements have found an anomaly in the cosmic-ray energy spectrum at GeV-TeV energies. Although the origin of the anomaly is not clearly understood, suggested explanations include effect of cosmic-ray source spectrum, propagation effects, and the effect of nearby sources. In this paper, we propose that the spectral anomaly might be an effect of re-acceleration of cosmic rays by weak shocks in the Galaxy. After acceleration by strong supernova remnant shock waves, cosmic rays undergo diffusive propagation through the Galaxy. During the propagation, cosmic rays may again encounter expanding supernova remnant shock waves, and get re-accelerated. As the probability of encountering old supernova remnants is expected to be larger than the younger ones due to their bigger sizes, re-acceleration is expected to be mainly due to weaker shocks. Since weaker shocks generate a softer particle spectrum, the resulting re-accelerated component will have a spectrum steeper than the initial cosmic-ray source spectrum produced by strong shocks. For a reasonable set of model parameters, it is shown that such re-accelerated component can dominate the GeV energy region while the non-reaccelerated component dominates at higher energies, explaining the observed GeV-TeV spectral anomaly. Show Chinese abstract

Abstract: 近期的宇宙射线测量发现，在GeV-TeV能区的宇宙射线能量谱中存在一个异常现象。尽管该异常的起源尚不清楚，但可能的解释包括宇宙射线源谱效应、传播效应以及附近源的影响。 本文提出，这种谱系异常可能是银河系弱激波对宇宙射线重新加速的结果。在被超新星遗迹强激波加速后，宇宙射线通过银河系进行扩散传播。在此过程中，宇宙射线可能会再次遇到膨胀的超新星遗迹激波，并被重新加速。由于预期遇到较老超新星遗迹的概率大于较年轻的超新星遗迹（因为它们体积更大），因此重新加速主要由较弱的激波引起。而较弱的激波会生成较软的粒子谱，从而导致重新加速后的成分具有比由强激波产生的初始宇宙射线源谱更陡峭的能谱。对于一组合理的模型参数，研究表明，这种重新加速的成分可以在GeV能区占主导地位，而非重新加速的成分则在更高能量占主导地位，这可以解释观测到的GeV-TeV谱系异常。