Spatial location of variables for a cell with indices (i, j, k), correspondent to directions (x, y, z), respectively. Line integrals of the electric field ℰ are located at its edges, and magnetic and numerical fluxes Φ and Fⁱ (the latter used for the BS algorithm) are located at its faces. The conserved hydrodynamic variables belonging to the array U, are located at cell centers (not shown).