Speakers
Description
Cosmic ray particles reach energies as high as $10^{21}\,$eV, and most likely they are accelerated in varying electromagnetic fields present in astrophysical sources and the interstellar medium. Most promising acceleration mechanisms are the First and Second Order Fermi acceleration: Cosmic ray particles repeatedly scatter on moving magnetic field turbulences and on average they gain energy from these collisions.
I present how the First order mechanism, also referred to as Diffusive Shock Acceleration, can be modelled with CRPropa using the DiffusionSDE Module. Particles are accelerated when they diffuse over the shock and experience a changing flow velocity. Changes in the advective field and the diffusion coefficient over the shock are approximated by differentiable functions that can be handled by DiffusionSDE. With this approach, the resulting CR spectrum highly depends on the choice of the "shock width" and the step length of the simulation.
In addition, I give an outlook how the Second order mechanism, also referred to as Momentum Diffusion, can be modelled by stochastic differential equations. The modelling of Diffusive Shock Acceleration and Momentum Diffusion extend CRPropa's Acceleration Module to diffusive transport.
