The status and challenges of MHD modeling in xRAGE

Magnetohydrodynamics (MHD) is relevant for fields such as internal confinement fusion (ICF) and high energy density (HED) physics. Inclusion of MHD in xRage and other hydro codes is a nontrivial exercise. To further complicate things, xRage is different from many other codes due to it’s essentially unstructured, cell-based AMR mesh. As a result of this, methods which are documented for other codes may be incompatible. For example, in xRage, the construction of discrete stencils on staggered grids is more complex than in a code with block-based AMR. These differences are particularly troublesome in calculations for values relevant to MHD (such as current) at AMR refinement boundaries. Furthermore, due to the small timesteps required for some facets of MHD, an operator split implicit time integration method is necessary for these terms. Implicit time integration further compounds these difficulties along AMR boundaries. In this talk I will discuss MHD in xRage and the unique challenges in its implementation. Finally, I will also discuss the complications associated with implementing extended MHD terms like Nernst, Biermann battery, and Hall in the xRage hydro code.