Velocity decorrelation functions of high-energy cosmic rays propagating in magnetic fields

Abstract

Diffusion tensor coefficients play a central role in describing cosmic-ray transport in various astrophysical environments permeated with magnetic fields, which are usually modeled as a fluctuating field on top of a mean field. In this article, a formal derivation of these coefficients is presented by means of the calculation of velocity decorrelation functions of particles. It relies mainly on expanding the 2-pt correlation function of the (fluctuating) magnetic field experienced by the particles between two successive times in the form of an infinite Dyson series and retaining a class of terms that converge to a physical solution. Subsequently, the velocity decorrelation functions, themselves expressed as Dyson series, are deduced from an iteration procedure that improves on the partial summation scheme. The results are shown to provide approximate solutions compared to those obtained by Monte-Carlo simulations as long as the Larmor radius of the particles is larger than at least one tenth of the largest scale of the turbulence.

15 pages, 11 figures, accepted for publication in Phys. Rev. D

References in corpus (9)

• Feedback Heating by Cosmic Rays in Clusters of Galaxies
• Cosmic ray physics in calculations of cosmological structure formation
• Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition
• Charged particle diffusion in isotropic random magnetic fields
• Simulating Gamma-ray Emission in Star-forming Galaxies
• First Predicted Cosmic Ray Spectra, Primary-to-Secondary Ratios, and Ionization Rates from MHD Galaxy Formation Simulations
• Particle Transport in intense small scale magnetic turbulence with a mean field
• The impact of astrophysical dust grains on the confinement of cosmic rays
• Numerical Study of Cosmic Ray Confinement through Dust Resonant Drag Instabilities