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T: Fachverband Teilchenphysik

T 103: Cosmic rays IV

T 103.3: Vortrag

Freitag, 3. April 2020, 11:30–11:45, L-3.002

Deepening the understanding of cosmic-ray diffusion — •Patrick Reichherzer1,2,3, Julia Tjus1,2, Ellen Zweibel4, Lukas Merten5, and M.J. Pueschel61Ruhr-University Bochum, Theoretical Physics IV — 2Ruhr Astroparticle and Plasma Physics (RAPP) Center — 3Irfu,CEA Paris-Saclay — 4Department of Astronomy & Physics, University of Wisconsin-Madison — 5Institute for Astro-& Particle Physics, University of Innsbruck — 6Institute for Fusion Studies, University of Texas at Austin

Understanding the transport of energetic cosmic rays belongs to the most challenging topics in astrophysics. The complicated evolution of the cosmic-ray distribution can be modeled mathematically by a diffusive process in the limit of large times. Consequently, diffusion is of fundamental importance in the transport of cosmic rays through turbulence.

We demonstrate the reduction of numerical artifacts for the calculation of the diffusion coefficient D by providing important conditions for physical and numerical input parameters. We characterize the rigidity regimes of D for arbitrary rigidities and guide fields, which we derive as a function of physical and numerical parameters. We show that at turbulence levels b/B above 5% of the total magnetic field, the approximation of an energy dependence 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 b/B-dependent diffusion coefficient and can contribute to solving the Galactic cosmic-ray gradient problem.

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