Phan Vo Hong Minh, Schulze Florian, Mertsch Philipp, Recchia Sarah, Gabici Stefano
Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, Aachen 52056, Germany.
Université de Paris, CNRS, Astroparticule et Cosmologie, Paris F-75006, France.
Phys Rev Lett. 2021 Oct 1;127(14):141101. doi: 10.1103/PhysRevLett.127.141101.
Data from the Voyager probes have provided us with the first measurement of cosmic ray intensities at MeV energies, an energy range that had previously not been explored. Simple extrapolations of models that fit data at GeV energies, e.g., from AMS-02, however, fail to reproduce the Voyager data in that the predicted intensities are too high. Oftentimes, this discrepancy is addressed by adding a break to the source spectrum or the diffusion coefficient in an ad hoc fashion, with a convincing physical explanation yet to be provided. Here, we argue that the discrete nature of cosmic ray sources, which is usually ignored, is instead a more likely explanation. We model the distribution of intensities expected from a statistical model of discrete sources and show that its expectation value is not representative but has a spectral shape different from that for a typical configuration of sources. The Voyager proton and electron data are however compatible with the median of the intensity distribution.
“旅行者号”探测器传回的数据为我们提供了对兆电子伏特能量下宇宙射线强度的首次测量结果，此前该能量范围尚未被探索过。然而，简单外推适用于千兆电子伏特能量数据的模型（例如来自阿尔法磁谱仪-02的数据），无法再现“旅行者号”的数据，因为预测的强度过高。通常，这种差异是通过以特设方式在源谱或扩散系数中添加一个断点来解决的，而尚未给出令人信服的物理解释。在这里，我们认为通常被忽略的宇宙射线源的离散性质反而更有可能是一个解释。我们对离散源统计模型预期的强度分布进行建模，并表明其期望值不具有代表性，而是具有与典型源配置不同的光谱形状。不过，“旅行者号”的质子和电子数据与强度分布的中位数是相符的。
