MHD Simulations of a Supernova-driven ISM

We present new 3D magnetohydrodynamic (MHD) simulations of a supernova-driven, stratified ISM. We have previously shown that the density distribution arising from hydrodynamic (HD) versions of these simulations creates lowdensity pathways through which Lyman continuum photons can travel to heights |z| > 1 kpc. This naturally produces the warm ionized medium through photoionization due primarily to O stars near the plane. However, the HD models reproduce the peak but not the width of the emission measure distribution observed in Wisconsin H-Alpha Mapper (WHAM) data. Here, we discuss the role of magnetic fields in the structure of gas away from the plane.