Diffusive Origin of the Cosmic-Ray Spectral Hardening

TL;DR

This paper proposes that the observed spectral hardening of cosmic rays at high energies can be explained by spatial variations in diffusion properties within the Galaxy, challenging conventional models.

Contribution

It introduces a new explanation for cosmic-ray spectral hardening based on spatially changing diffusion coefficients, supported by analytical calculations.

Findings

Spectral hardening explained by spatial diffusion variations

Implications for cosmic-ray observables discussed

Connects diffusion changes with open CR physics issues

Abstract

Recent data from ATIC, CREAM and PAMELA revealed that the energy spectra of cosmic ray (CR) nuclei above 100 GeV/nucleon experience a remarkable hardening with increasing energy. This effect cannot be recovered by the conventional descriptions of CR acceleration and diffusive propagation processes. Using analytical calculations, I show that the hardening effect can be consequence of a spatial change of the CR diffusion properties in different regions of the Galaxy. I discuss the implications of this scenario for the main CR observables and its connections with the open issues of the CR physics.