# Non-linear Cosmic Ray Propagation

## TL;DR

This paper explores how non-linear effects in cosmic ray propagation, including wave generation and induced galactic winds, influence cosmic ray spectra and may explain recent spectral anomalies.

## Contribution

It introduces the concept that non-linear effects on galactic scales significantly impact cosmic ray transport and spectral features, advancing understanding beyond linear models.

## Key findings

- Non-linear wave generation affects cosmic ray scattering.
- Galactic winds driven by cosmic rays alter propagation.
- Spectral anomalies may be explained by non-linear effects.

## Abstract

The description of the transport of cosmic rays in magnetized media is central to both acceleration and propagation of these particles in our Galaxy and outside. The investigation of the process of particle acceleration, especially at shock waves, has already emphasized that non-linear effects such as self-generation of waves and dynamical reaction of cosmic rays on the background plasmas, are crucial if to achieve a physical understanding of the origin of cosmic rays. Here we discuss how similar non-linear effects on Galactic scales may affect the propagation of cosmic rays, not only through the excitation of plasma waves important for particle scattering, but also by inducing the motion of the interstellar medium in the direction opposite to the gravitational pull exerted by matter in the Galaxy, thereby resulting in the launching of a wind. The recent discovery of several unexpected features in cosmic ray spectra (discrepant hardening, spectral breaks in the H and He spectra, rising positron fraction and unexpectedly hard antiproton spectrum) raises the question of whether at least some of these effects may be attributed to poorly understood aspects of cosmic ray transport.