Secondary cosmic ray nucleus spectra strongly favor reacceleration of particle transport in the Milky Way

Abstract

The precise observations of Galactic cosmic ray fluxes of the secondary family, such as Li, Be, B, are expected to have significant implications on our understanding of the cosmic ray origin and propagation. Here we employ the recent very precise measurements of those species by the Alpha Magnetic Spectrometer on the International Space Station, together with their parent species (C and O), as well as the data collected by the Voyager-1 spacecraft outside the heliosphere and the Advanced Composition Explorer, we investigate the propagation of cosmic rays in the Milky Way. We find that these new data strongly favor the existence of reacceleration of cosmic rays during the propagation rather than the convective transport. We further find that for the reacceleration model, the slope of rigidity dependence of the diffusion coefficient is close to the Kolmogorov-type of turbulence, and the spectral hardenings of both the primary and secondary particles can be well described by the injection hardening rather than the propagation hardening.