Observation of High Energy Cosmic Rays below 10[sup 17] eV

The shape and composition of the primary spectrum as well as the anisotropy in the arrival direction of cosmic rays are key elements to understand the origin, acceleration and propagation of the galactic radiation. A more refined generation of satellites, balloon experiments, and ground‐based detectors was recently developed and operated to address such problems at energies below 1017 eV. The general picture that comes out from their results indicate that the cosmic ray spectrum has a more complex shape than a simple smooth double power law E−γ with a break around 3–4×1015 eV. The proton spectrum seems to be softer than the other primaries in the GeV‐TeV range; a significant medium and large scale anisotropy exists around 2–20 TeV. Just above the knee the spectrum shows a small concavity, and around 50–100 PeV another small but statistically significant structure.