Indication of nearby source signatures of cosmic rays from energy spectra and anisotropies

Abstract

The origin of Galactic cosmic rays (GCRs) remains a mystery after more than one century of their discovery. The diffusive propagation of charged particles in the turbulent Galactic magnetic field makes us unable to trace back to their acceleration sites. Nevertheless, nearby GCR source(s) may leave imprints on the locally measured energy spectra and the anisotropies of the arrival direction. In this work we propose a simple but natural description of the GCR production and propagation, within a two-zone disk-halo diffusion scenario together with a nearby source, to understand the up-to-date precise measurements of the energy spectra and anisotropies of GCRs. We find that a common energy scale of ∼100 TeV appears in both energy spectra of protons and helium nuclei measured recently by CREAM and large-scale anisotropies detected by various experiments. These results indicate that one or more local sources are very likely important contributors to GCRs below 100 TeV . This study provides a probe to identify source(s) of GCRs by means of joint efforts of spectral and anisotropy measurements.