Cosmic ray spectrum and anisotropies from the knee to the second knee

Abstract

We consider the scenario in which the knee in the cosmic ray spectrum is due to a change in the escape mechanism of cosmic rays from the Galaxy from one dominated by transverse diffusion to one dominated by drifts. We show that this scenario explains not only the changes in spectral slope at the knee and at the second knee, but can also account for the main characteristics of the observed energy-dependent anisotropy amplitude and phase of first harmonic in the energy range between 10¹⁵ and 10¹⁸ eV. This provides a useful handle to distinguish this diffusion/drift model from other scenarios proposed to explain the knee in the spectrum.