Implications of turbulence-dependent diffusion on cosmic-ray spectra

TL;DR

This paper explores how turbulence-dependent diffusion models can explain the observed cosmic-ray density gradients and spectral behaviors in the Milky Way, challenging existing models.

Contribution

It introduces a turbulence-dependent diffusion model that accounts for cosmic-ray propagation and explains observed galactic gradients and spectra.

Findings

Turbulence-dependent diffusion can reproduce observed cosmic-ray gradients.

Energy-scaling of the diffusion tensor explains spectral variations.

Model aligns with gamma-ray observations from Fermi.

Abstract

The propagation of cosmic rays can be described as a diffusive motion in most galactic environments. High-energy gamma-rays measured by Fermi have allowed inference of a gradient in the cosmic-ray density and spectral energy behavior in the Milky Way, which is not predicted by models. Here, a turbulence-dependent diffusion model is used to probe different types of cosmic-ray diffusion tensors. Crucially, it is demonstrated that the observed gradients can be explained through turbulence-dependent energy-scaling of the diffusion tensor.