The spectrum of high-energy cosmic rays measured with KASCADE-Grande

The energy spectrum of cosmic rays between 1016 eV and 1018 eV, derived from measurements of the shower size (total number of charged particles) and the total muon number of extensive air showers by the KASCADE-Grande experiment, is described. The resulting all-particle energy spectrum exhibits strong hints for a hardening of the spectrum at approximately 2 · 1016 eV and a significant steepening at ≈8 · 1016 eV. These observations challenge the view that the spectrum is a single power law between knee and ankle. Possible scenarios generating such features are discussed in terms of astrophysical processes that may explain the transition region from galactic to extragalactic origin of cosmic rays.

► All-particle energy spectrum of cosmic rays between knee and ankle is not a single power law.
► Just above 1016 eV the spectrum exhibits a hardening.
► Around 8 × 1016 eV there is a knee-like feature in the spectrum.