PropPy is an open-source python software for propagating charged high-energy particles (cosmic rays) in a turbulent magnetic field. Its modular architecture comprises various sources, magnetic fields, propagators, observers, and analyzing modules covering a wide range of applications. Here, propagation is based on a correlated random walk (CRW) in Cartesian (for isotropic diffusion) or cylindrical (for anisotropic diffusion) coordinates, which makes each simulation step significantly faster than comparable codes that have to solve the equation of motion in each propagation time. This novel approach is justified by the fact that a transport equation can be derived via the formulation of the CRW, which is used in analytical descriptions of particle transport. This makes PropPy a high-performance software for the simulation of charged particles in turbulent magnetic fields, especially for compact objects and transient events with short time scales, such as gamma-ray bursts, active galactic nuclei flares, where the accurate description of the initial particle propagation is crucial.

Peer-reviewed in JOSS