Self-generated magnetic turbulence and the propagation of galactic cosmic rays

TL;DR

This paper models how cosmic rays generate magnetic turbulence in the galaxy, affecting their diffusion and resulting in predictions that match observed cosmic ray spectra and composition.

Contribution

It presents a self-consistent model combining self-generated and preexisting turbulence to explain cosmic ray propagation and secondary-to-primary ratios.

Findings

Predicted cosmic ray spectra match observations

Secondary to primary ratios are accurately reproduced

Self-generated turbulence significantly influences cosmic ray diffusion

Abstract

Cosmic rays propagating in the Galaxy may excite a streaming instability when their motion is super-alfvenic, thereby producing the conditions for their own diffusion. We present the results of a self-consistent solution of the transport equation where diffusion occurs because of the self-generated turbulence together with a preexisting turbulence injected, for instance, by supernova explosions and cascading to smaller scales. All chemicals are included in our calculations, so that we are able to show the secondary to primary ratios in addition to the spectra of the individual elements. All predictions appear to be in good agreement with observations.