Angular distribution of cosmic rays from an individual source in a turbulent magnetic field

TL;DR

This paper models how cosmic rays from a single source are distributed in angle after traveling through turbulent magnetic fields, considering different energy regimes, energy losses, and magnetic lensing effects.

Contribution

It provides a comprehensive analysis of cosmic ray angular distributions accounting for turbulence, energy losses, and magnetic lensing, bridging rectilinear and diffusive propagation regimes.

Findings

Energy losses increase anisotropy at fixed energy.

Turbulent magnetic fields smooth out lensing magnification peaks.

The model covers both high-energy rectilinear and low-energy diffusive regimes.

Abstract

We obtain the angular distribution of the cosmic rays reaching an observer from an individual source and after propagation through a turbulent magnetic field, for different ratios between the source distance and the diffusion length. We study both the high-energy quasi-rectilinear regime as well as the transition towards the diffusive regime at lower energies where the deflections become large. We consider the impact of energy losses, showing that they tend to enhance the anisotropy of the source at a given energy. We also discuss lensing effects, in particular those that could result from the regular galactic magnetic field component, and show that the effect of the turbulent extragalactic magnetic fields can smooth out the divergent magnification peaks that would result for point-like sources in the limit of no turbulent deflections.