Deepening the understanding of cosmic-ray diffusion. (arXiv:1910.07528v1 [astro-ph.HE])

Deepening the understanding of cosmic-ray diffusion. (arXiv:1910.07528v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Reichherzer_P/0/1/0/all/0/1">P. Reichherzer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tjus_J/0/1/0/all/0/1">J. Becker Tjus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zweibel_E/0/1/0/all/0/1">E.G. Zweibel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Merten_L/0/1/0/all/0/1">L. Merten</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pueschel_M/0/1/0/all/0/1">M.J. Pueschel</a>

For the first time, we characterize the rigidity regimes of the diffusion
coefficient $kappa$ for arbitrary rigidities and guide fields, which we derive
as a function of physical and numerical parameters. We show that at turbulence
levels above 5% of the total magnetic field, the approximation of an energy
dependence $kappapropto E^{1/3}$ as predicted for a Kolmogorov spectrum
within Quasi-Linear Theory does not hold. Consequently, a proper description of
cosmic-ray propagation can only be achieved by using a turbulence-level
dependent diffusion coefficient and can contribute to solving the Galactic
cosmic-ray gradient problem.

For the first time, we characterize the rigidity regimes of the diffusion
coefficient $kappa$ for arbitrary rigidities and guide fields, which we derive
as a function of physical and numerical parameters. We show that at turbulence
levels above 5% of the total magnetic field, the approximation of an energy
dependence $kappapropto E^{1/3}$ as predicted for a Kolmogorov spectrum
within Quasi-Linear Theory does not hold. Consequently, a proper description of
cosmic-ray propagation can only be achieved by using a turbulence-level
dependent diffusion coefficient and can contribute to solving the Galactic
cosmic-ray gradient problem.

http://arxiv.org/icons/sfx.gif