Implications on the origin of cosmic rays in light of 10 TV spectral softenings

Abstract

Precise measurements of the energy spectra of cosmic rays (CRs) show various kinds of features deviating from single power-laws, which give very interesting and important implications on their origin and propagation. Previous measurements from a few balloon and space experiments indicate the existence of spectral softenings around 10 TV for protons (and probably also for Helium nuclei). Very recently, the DArk Matter Particle Explorer (DAMPE) measurement about the proton spectrum clearly reveals such a softening with a high significance. Here we study the implications of these new measurements, as well as the groundbased indirect measurements, on the origin of CRs. We find that a single component of CRs fails to fit the spectral softening and the air shower experiment data simultaneously. In the framework of multiple components, we discuss two possible scenarios, the multiple source population scenario and the background plus nearby source scenario. Both scenarios give reasonable fits to the wide-band data from TeV to 100 PeV energies. Considering the anisotropy observations, the nearby source model is favored.

Anisotropies of different mass compositions of cosmic rays

“…Hints of such spectral features were also found previously by CREAM [23] and NUCLEON measurements [24]. These new observations indicate that the structures of the energy spectra of CRs are more complicated than expected (see e.g., [25,26] for discussions).…”

Hybrid origins of the cosmic-ray nuclei spectral hardening at a few hundred GV

“…As some previous work have been pointed out (see, e.g., Refs. [28,[41][42][43]), it could be naturally explained by the superposition of different kinds of sources. In this scenario, each kind of the sources have similar spectral indexes for all the primary source injection but have different element abundances between different kinds of sources.…”

Recent status and results of the Dark Matter Particle Explorer

“…A smoothly broken power-law fit gives that the spectral index changes from −2.60 to −2.85 at 13.6 +4.1 −4.8 TeV for proton and from −2.41 to −2.92 at 34.4 +6.7 −9.8 TeV for helium. These softenings feature may have very interesting implication in modeling the origin and propagation of CRs (e.g., [45][46][47]).…”