Localized Galactic sources and their contribution beyond the second knee

TL;DR

This paper investigates the contribution of localized galactic sources to cosmic rays beyond the second knee, using a diffusion model focused on the inner Galaxy and spiral arm structure.

Contribution

It introduces a two-dimensional diffusion model to analyze localized supernova contributions and their role in cosmic ray flux at high energies.

Findings

Localized sources may significantly contribute beyond the second knee.

Spiral arm structure influences cosmic ray propagation.

Inner Galaxy regions are crucial for understanding high-energy cosmic rays.

Abstract

The energy range encompassing the ankle of the cosmic ray energy spectrum probably marks the exhaustion of the accelerating sources in our Galaxy, as well as the end of the Galactic confinement. Furthermore, this is the region where the extragalactic flux penetrates the interstellar medium and starts, progressively, to be dominant. Although at lower energies it is likely that an "average" population of supernova remnants can be defined to account for most of the cosmic ray flux, this assumption is increasingly difficult to maintain as higher energies are considered. One possibility is that supernovas are still a main contributor along the first branch of the ankle region, but that the acceleration is now coming from well localized regions with a characteristic interstellar medium, or a sub-population of supernovas exploding in a peculiar circumstellar environment. These possibilities are analyzed in the present work using a two-dimensional diffusion model for cosmic ray propagation. Special emphasis is given to the inner 200 pc of our Galaxy and to the spiral arm structure in relation with the Sun position inside the disk.