  The role of slow-mode MHD shocks in magnetic reconnection is one of great
importance for energy conversion and transport, but in many astrophysical
plasmas the plasma is not fully ionised. In this paper, we investigate, using
numerical simulations, the role of collisional coupling between a
proton-electron charge-neutral fluid and a neutral hydrogen fluid for the 1D
Riemann problem initiated in a constant pressure and density background state
by a discontinuity in the magnetic field. This system, in the MHD limit, is
characterised by two waves: a fast-mode rarefaction wave that drives a flow
towards a slow-mode MHD shock. The system evolves through four stage:
initiation, weak coupling, intermediate coupling and a quasi steady state. The
initial stages are characterised by an over-pressured neutral region that
expands with characteristics of a blast wave. In the later stages, the system
tends towards a self-similar solution where the main drift velocity is
concentrated in the thin region of the shock front. Due to the nature of the
system, the neutral fluid is overpressured by the shock when compared to a
purely hydrodynamic shock which results in the neutral fluid expanding to form
the shock precursor. The thickness of the shockfront once it has formed
proportional to the ionisation fraction to the power -1.2, which is a smaller
exponent than would be naively expected from simple scaling arguments. One
interesting result is that the shock front is a continuous transition of the
physical variables for sub-sonic velocity upstream of the shock front (a
c-shock) to a sharp jump in the physical variables followed by a relaxation to
the downstream values for supersonic upstream velocity (a j-shock). The
frictional heating that results from the velocity drift across the shock front
can amount to approximately two per cent of the reference magnetic energy.
