Escape model for Galactic cosmic rays

International audienceWe show that the cosmic ray (CR) knee can be entirely explained by energy-dependent CR leakage from the Milky Way, with an excellent fit to all existing data. We test this hypothesis calculating the trajectories of individual CRs in the Galactic magnetic field. We find that the CR escape time τesc(E) exhibits a knee-like structure around E/Z = few × 1015 eV for small coherence lengths and strengths of the turbulent magnetic field. The resulting intensities for different groups of nuclei are consistent with the ones determined by KASCADE and KASCADE-Grande, using simple power-laws as injection spectra. The transition from Galactic to extragalactic CRs is terminated at ≈ 2×1018 eV, while extragalactic CRs contribute significantly to the subdominant proton flux already for >∼ 2×1016 eV. The natural source of extragalactic CRs in the intermediate energy region up to the ankle are in this model normal and starburst galaxies. The escape model provides a good fit to ln(A) data; it predicts that the phase of the CR dipole varies strongly in the energy range between 1×1017 and 3×1018 eV, while our estimate for the dipole magnitude is consistent with observations. above E > 1014 eV. Adding a single nearby source to this model explains moreover the dipole anisotropy below 1014 eV, the specific slope of the locally measured proton flux as well as of the antiproton and positron fluxes