Its the latter bit that seems so mind bending to me. MHD simulations start with a plasma and it can be conducting throughout the simulation in all places.
CFD simulations deal with the forces between elements that express as viscosity, turbulent, and laminar flows.
MHD assumes that elements in the flow are always affected by the electro-magnetic forces in play, CFD doesn't account for electro-magnetic forces.
CFD assumes that the elements in the flow are only affected by the forces of nearby elements and not the actions or state of elements that are further away.
An FeO simulation has to combine them somehow, and account for whorls and eddies converting elements from the MHD domain into the CFD domain and then back again.
Anyway, I am looking forward to the papers on this stuff. It combines two areas I enjoy, complex systems and physics!