Coupling the two-fluid/Maxwell system to Magnetohydrodynamics/Ohm’s law

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Astrophysical and space plasmas can be considered to be collisionless. The spatial and temporal scales occurring in such plasmas span more than 7 orders of magnitude from the finest kinetic to the global scales. Therefore, a multiscale/multiphysics modelling of plasmas is essential.In this project we consider the surface coupling of the two-fluid/Maxwell with the magneto-hydrodynamic (MHD) description. The transition from the two-fluid/maxwell to the MHD description contains several singular limits: i) the speed of light tends to infinity, ii) the ratio of Debye to system length vanishes and the electron mass is neglected. This leads to interesting questions when coupling MHD to the two-fluid/Maxwell system, such as: i) How can the information missing in the MHD be "reconstructed" to define consistent fluxes at the boundaries of the two descriptions? ii) How can a consistent energy density be formulated? iii) How can refinement criteria be defined to indicate when the MHD description is no longer appropriate? All these questions will be addressed in this project.This project is part of the DFG research unit "Structure-Preserving Numerical Methods for Bulk- and Interface-Coupling of Heterogeneous Models (SNuBIC)".