The goals of this proposal are to characterize the physical nature and
emergent spectrum of low velocity (v<15-20 km/sec) shocks in the dense
interstellar medium and to test models of MHD shocks in the low velocity
range where they are hitherto untested.  High velocity MHD shocks from
protostellar outflows, Herbig-Haro objects, and supernova remnants have
been studied extensively from the ground in optical and IR lines. There
are already good plans for studies of such objects in the ISO Central
Program.  There is no corresponding plan to study low velocity shocks.

Low velocity shocks are important as signposts of injection and
dissipation of turbulent energy in the dense ISM.  We expect to see
emission from such shocks in three contexts:  swept-up or entrained gas
in protostellar flows, gas shocked ahead of HII ionization fronts, and
clouds with high velocity dispersions.  The first two represent possible
sources for injection of kinetic energy into clouds.  The third type of
shock may be a result of dissipation of internal motion.

We will examine a small sample of protostellar flows and turbulent
clouds in the OI 63 micron line and several ground state rotational
transitions of H2.  The targets have been chosen to avoid regions
with high velocity shocks or strong PDR emission.  We will test for
PDR contamination with CII observations and ground-based H2
observations.