The “Theory and Simulation of Solar System Plasmas” session solicits presentations of the latest results from theoretical investigations and numerical simulations in space plasma-physics from microscopic to global scales, in comparison with experiments and observations in the heliosphere: at the Sun, in the solar corona, in interplanetary space and in planetary magnetospheres. Each year a topic of special interest is chosen as a focus of the session. For 2019 this focus will be on the sun. Of particular interest is to understand plasma heating and particle acceleration processes as well as the resulting observable radiation processes. We encourage presentations of theory and modelling results directly relevant to current and forthcoming space missions, notably MMS, the Parker Solar Probe, Solar Orbiter and Bepi Colombo