With the breakthrough in PeV gamma-ray astronomy brought by the LHAASO experiment, the high-energy sky is getting richer than before. Lately, LHAASO Collaboration reported the observation of a gamma-ray diffuse emission with energy up to the PeV level from both the inner and outer Galactic plane. In these spectra, there is one bump that is hard to explain by the conventional cosmic-ray...
The origin of the knee structure in cosmic ray (CR) energy spectrum remains unresolved. Various types of models have been proposed to explain it, which can be distinguished as acceleration origin (due to the limitation of the maximum possible CR energy by Galactic sources), propagation origin (because of the transition from slow to fast diffusion of Galactic CRs), interaction origin and local...
