  The collision of two plasma clouds at a speed that exceeds the ion acoustic
speed can result in the formation of shocks. This phenomenon is observed not
only in astrophysical scenarios such as the propagation of supernova remnant
(SNR) blast shells into the interstellar medium, but also in laboratory-based
laser-plasma experiments. These experiments and supporting simulations are thus
seen as an attractive platform for the small-scale reproduction and study of
astrophysical shocks in the laboratory. We model two plasma clouds, which
consist of electrons and ions, with a 2D PIC simulation. The ion temperatures
of both clouds differ by a factor of 10. Both clouds collide at a speed, which
is realistic for laboratory studies and for SNR shocks in their late evolution
phase like that of RCW86. A magnetic field, which is orthogonal to the
simulation plane, has a strength that is comparable to that at SNR shocks. A
forward shock forms between the overlap layer of both plasma clouds and the
cloud with the cooler ions. A large-amplitude ion acoustic wave is observed
between the overlap layer and the cloud with the hotter ions. It does not
steepen into a reverse shock, because its speed is below the ion acoustic
speed. A gradient of the magnetic field amplitude builds up close to the
forward shock as it compresses the magnetic field. This gradient gives rise to
an electron drift that is fast enough to trigger an instability. Electrostatic
ion acoustic wave turbulence develops ahead of the shock. It widens its
transition layer and thermalizes the ions, but the forward shock remains
intact.
