EVOLUTION OF THE COSMIC-RAY ANISOTROPY ABOVE 10 14 eV

The amplitude and phase of the cosmic-ray anisotropy are well established experimentally between 10 11 eV and 10 14 eV. The study of their evolution in the energy region 10 14 –10 16 eV can provide a significant tool for the understanding of the steepening ("knee") of the primary spectrum. In this Letter, we extend the EAS-TOP measurement performed at E 0 ≈ 10 14 eV to higher energies by using the full data set (eight years of data taking). Results derived at about 10 14 and 4 × 10 14 eV are compared and discussed. Hints of increasing amplitude and change of phase above 10 14 eV are reported. The significance of the observation for the understanding of cosmic-ray propagation is discussed.