Multi-Ion Hall-MHD Formulation and Highly-Coupled Numerical Implementation into Hybrid Particle-in-Cell Code

A highly-coupled single-fluid two-temperature magnetohydrodynamic (MHD) algorithm has been outlined in C. Thoma, et al., Comp. Phys. Comm., 261 (2021) 107823. The Hall term is included in a natural way into the highly-coupled formulation. The extension of this algorithm to include an arbitrary number of MHD ion species is described. The algorithm now also allows for the coupling of highly-coupled MHD species with an arbitrary number of auxiliary non-MHD species. The algorithm has been implemented in the particle-in-cell code Chicago. These refinements to the model allow for greater flexibility, as distinct particle populations in a simulation may be represented either as kinetic, fluid, or MHD species. Migrations between kinetic, fluid, and MHD species can also be accommodated based on user-defined criteria. The implementation of the algorithm into Chicago is described, and some preliminary simulation results in 1D and 2D are given.