Cosmic-ray primary spectrum: dN/dE ∝ E^{−2.7} below knee, E^{−3.0} above

All-particle cosmic-ray differential flux follows a broken power-law. Below the 'knee' (~3·10¹⁵ eV = 3 PeV), dN/dE ∝ E^{−2.7}: galactic sources (supernova-remnant shock diffusive acceleration) with ~10% efficiency. Between knee and…