Towards a GPU based particle model for streamer discharges

Terrestrial gamma-ray flashes (TGFs), bursts of X- and gamma-rays, are emitted from thunderstorms and are produced through relativistic electrons through the Bremsstrahlung process. Despite recent progress through measurements and simulations, the specific mechanism of electron acceleration remains unknown. As the processes inside thunderclouds occur on a multiscale level, we need to develop models that cover a wide range of temporal and spatial scales. As a first step, we here present a GPU based Monte Carlo particle-in-cell code to simulate electron avalanches and streamers, benchmarked against existing particle models. We will present this benchmarking as well as details on the GPU-code implementation as well as first results of electron avalanches and streamers and compare runtimes with previous models. This code will form the basis for a fully hybrid code running on the newest generation of pre-exascale computers. In the future, such a code will allow us to gain insight on the mechanisms responsible for TGFs.