Stability of two-fluid partially ionized slow-mode shock fronts

A magnetohydrodynamic (MHD) shock front can be unstable to the corrugation instability, which causes a perturbed become increasingly corrugated with time. An ideal MHD parallel (where velocity and magnetic fields are aligned) is unconditionally whereas hydrodynamic (HD) counterpart stable. For partially ionised medium (for example solar chromosphere), both species coexist stability of system has not been studied. In this paper, we perform numerical simulations instability in two-fluid partially-ionised fronts investigate conditions, compare results HD simulations. Our consist an initially steady 2D encountering localised upstream density perturbation. MHD, perturbation grows We find that for simulation, neutral act stabilise front. parameter study performed analyse conditions under stable unstable. very weakly coupled or strongly unstable, as tends towards MHD. However, finite coupling, neutrals front, produce new features including channels species. derive equation relates wavelength range ion-neutral neutral-ion coupling frequencies Mach number. Applying relation umbral flashes give estimated wavelengths between 0.6 56 km.