Heidelberg 2022 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 12: Sun and Heliosphere

EP 12.7: Vortrag

Freitag, 25. März 2022, 13:00–13:15, EP-H1

Analytical and numerical methods for nonlinear diffusive transport and shock acceleration — •Dominik Walter¹, Horst Fichtner¹, Frederic Effenberger¹, and Yuri Litvinenko² — ¹Ruhr-Universität-Bochum; Institut theoretische Physik IV — ²University of Waikato, Department of Mathematics, New Zealand

We explore a nonlinear diffusive type of particle/cosmic ray transport. A special focus will be put on particles/cosmic rays, escaping from a shock or other localized acceleration sites and their acceleration process. Instead of solving coupled differential equations, as is the more common method of describing the interaction of diffusing particles with the backgrond medium, we analyse a single nonlinear advection-diffusion equation. In a first step we analyse the effect of the nonlinear model on particle transport, we apply an analytical expansion technique to cartesian and spherical symetrical geometries, to derive approximate solutions to the resulting equations and establish numerical models to compare and expand on this results. As a foundation for the numerical models we use the grid based Code VLUGR3, to provide numerical solutions, when there is no analytical way of solving distinct models. As a second step we construct a model for shock acceleration, to investigate the impact of nonlinear diffusion on shock acceleration, again using VLUGR3. We recreate a linear cartesian case of reference and use it as a groundwork to investigate the effects of nonlinearity.