  Plasma shock waves widely exist and play an important role in
high-energy-density environment, especially in the inertial confinement fusion.
Due to the large gradient of macroscopic physical quantities and the coupled
thermal, electrical, magnetic and optical phenomena, there exist not only
hydrodynamic non-equilibrium (HNE) effects, but also strong thermodynamic
non-equilibrium (TNE) effects around the wavefront. In this work, a
two-dimensional single-fluid discrete Boltzmann model is proposed to
investigate the physical structure of ion shock. The electron is assumed
inertialess and always in thermodynamic equilibrium. The Rankine-Hugoniot
relations for single fluid theory of plasma shock wave is derived. It is found
that the physical structure of shock wave in plasma is significantly different
from that in normal fluid and somewhat similar to that of detonation wave from
the sense that a peak appears in the front. The non-equilibrium effects around
the shock front become stronger with increasing Mach number. The charge of
electricity deviates oppositely from neutrality in upstream and downstream of
the shock wave. The large inertia of the ions causes them to lag behind, so the
wave front charge is negative and the wave rear charge is positive. The
variations of HNE and TNE with Mach number are numerically investigated. The
characteristics of TNE can be used to distinguish plasma shock wave from
detonation wave.
