Abstract Cosmicray transport in astrophysical environments is often dominated by the diffusion of particles in a magnetic field composed of both a turbulent and a mean component. This process, which is twofold turbulent mixing in that the particle motion is stochastic with respect to the field lines, needs to be understood in order to properly model cosmicray signatures. One of the most important aspects in the modeling of cosmicray diffusion is that fully resonant scattering, the most effective such process, is only possible if the wave spectrum covers the entire range of propagation angles. By taking the wave spectrum boundariesmore »
This content will become publicly available on June 21, 2023
Anisotropic cosmic ray diffusion in isotropic Kolmogorov turbulence
ABSTRACT Understanding the timescales for diffusive processes and their degree of anisotropy is essential for modelling cosmic ray transport in turbulent magnetic fields. We show that the diffusion timescales are isotropic over a large range of energy and turbulence levels, notwithstanding the high degree of anisotropy exhibited by the components of the diffusion tensor for cases with an ordered magnetic field component. The predictive power of the classical scattering relation as a description for the relation between the parallel and perpendicular diffusion coefficients is discussed and compared to numerical simulations. Very good agreement for a large parameter space is found, transforming classical scattering relation predictions into a computational prescription for the perpendicular component. We discuss and compare these findings, in particular, the timescales to become diffusive with the timescales that particles reside in astronomical environments, the socalled escape timescales. The results show that, especially at high energies, the escape times obtained from diffusion coefficients may exceed the timescales required for diffusion. In these cases, the escape time cannot be determined by the diffusion coefficients.
 Award ID(s):
 2007323
 Publication Date:
 NSFPAR ID:
 10348586
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 Volume:
 514
 Issue:
 2
 Page Range or eLocationID:
 2658 to 2666
 ISSN:
 00358711
 Sponsoring Org:
 National Science Foundation
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