SIMBAD references

Recent data on Galactic cosmic rays (CRs) revealed that the helium energy spectrum is harder than the proton spectrum. The AMS experiment has now reported that the proton-to-helium ratio as function of rigidity R (momentum-to-charge ratio) falls off steadily as p/He ∝R^Δ with Δ = -0.08 between R ∼ 40 GV and R ∼ 2 TV. Besides, the single spectra of proton and helium are found to progressively harden at R ≳ 100 GV. The p/He anomaly is generally ascribed to particle-dependent acceleration mechanisms occurring in Galactic CR sources. However, this explanation poses a challenge to the known mechanisms of particle acceleration since they are believed to be ''universal,'' composition-blind rigidity mechanisms. Using the new AMS data, we show that the p/He anomaly can be simply explained in terms of a two-component scenario where the GeV-TeV flux is ascribed to a hydrogen-rich source, possibly a nearby supernova remnant, characterized by a soft acceleration spectrum. This simple idea provides a common interpretation for the p/He ratio and for the single spectra of proton and helium: both anomalies are explained by a flux transition between two components. The ''universality'' of particle acceleration in sources is not violated in this model. A distinctive signature of our scenario is the high-energy flattening of the p/He ratio at multi-TeV energies, which is hinted at by existing data and will be resolutely tested by new space experiments ISS-CREAM and CALET.