A stochastic approach to galactic propagation

We present a newly developed numerical code solving general Fokker-Planck type transport equations by means of stochastic differential equations in four (space and momentum) dimensions and time. Besides propagation the code is capable of describing the full diffusion tensor as well as particle sources and sinks. The approach was to design the code very general and flexible, so that it can be applied to a large variety of physical problems. Adaption to graphics cards within the CUDA framework significantly improves the performance. Here, we apply our code to the propagation of cosmic ray protons in the Galaxy. Special account is devoted to the spiral arm structure and the consequence for turbulence and, thus, for the diffusion process, leading to different diffusion tensors within and outside of the spiral arms.