Würzburg 2018 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 11: Sun and Heliosphere III - Particles

EP 11.2: Talk

Thursday, March 22, 2018, 15:30–15:45, BSZ - Pabel HS

Nonlinear Diffusion and Anomalous Transport of Cosmic Rays — •Horst Fichtner¹, Yuri Litvinenko², and Dominik Walter¹ — ¹Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik IV, Univesitaetsstrasse 150, 44780 Bochum — ²Department of Mathematics, University of Waikato, P. B. 3105, Hamilton 3240, New Zealand

We investigate analytically and numerically the transport of cosmic rays away from a shock or another localized acceleration site. Observed cosmic-ray distributions in the vicinity of heliospheric shocks imply that anomalous, superdiffusive transport plays a role in the propagation of energetic particles. Previously, anomalous diffusion scalings, as implied by the data, have been quantitatively described with solutions of a fractional transport, although the physical basis of the fractional diffusion model remains uncertain. We explore an alternative model of the cosmic-ray transport: a nonlinear diffusion equation that follows from a self-consistent treatment of the resonantly interacting cosmic-ray particles and their self-generated turbulence. The nonlinear model naturally leads to superdiffusive scalings, and in the presence of convection, it yields a power-law dependence of the particle density on the distance upstream of the shock. The new solutions are tested by fitting them to spacecraft measurements.