  We study several mathematical aspects of a system of equations modelling the
interaction between short waves, described by a nonlinear Schr\"{o}dinger
equation, and long waves, described by the equations of magnetohydrodynamics
for a compressible, heat conductive fluid. The system in question models an
aurora-type phenomenon, where a short wave propagates along the streamlines of
a magnetohydrodynamic medium. We focus on the one dimensional (planar) version
of the model and address the problem of well posedness as well as convergence
of the sequence of solutions as the bulk viscosity tends to zero together with
some other interaction parameters, to a solution of the limit decoupled system
involving the compressible Euler equations and a nonlinear Schr\"{o}dinger
equation. The vanishing viscosity limit serves to justify the SW-LW
interactions in the limit equations as, in this setting, the SW-LW interactions
cannot be defined in a straightforward way, due to the possible occurrence of
vacuum.
