What do you want from your plasma simulation?

Selecting a plasma simulation tool is an exercise in compromise. Naïve application of the many tools available will in the best-case result in computationally expensive results. In the worst case, it will give gibberish results. In the first part of this talk I will give a high-level overview of the hierarchy of models and explain when they might be used. I’ll then share results from continuum plasma simulations of the Richtmyer-Meshkov instability to show how different the results might be for the same problem. In the second part of the talk, I will discuss the application of magnetohydrodynamics to the simulation of solar flares and coronal mass ejections. The goal of this work is the prediction of space-weather, the combined phenomena driven by solar eruptions that can damage space and terrestrial infrastructure as well as driving the beautiful auroras.