SHOCKFIND - An algorithm to identify magnetohydrodynamic shock waves in
  turbulent clouds
  The formation of stars occurs in the dense molecular cloud phase of the
interstellar medium. Observations and numerical simulations of molecular clouds
have shown that supersonic magnetised turbulence plays a key role for the
formation of stars. Simulations have also shown that a large fraction of the
turbulent energy dissipates in shock waves. The three families of MHD shocks
--- fast, intermediate and slow --- distinctly compress and heat up the
molecular gas, and so provide an important probe of the physical conditions
within a turbulent cloud. Here we introduce the publicly available algorithm,
SHOCKFIND, to extract and characterise the mixture of shock families in MHD
turbulence. The algorithm is applied to a 3-dimensional simulation of a
magnetised turbulent molecular cloud, and we find that both fast and slow MHD
shocks are present in the simulation. We give the first prediction of the
mixture of turbulence-driven MHD shock families in this molecular cloud, and
present their distinct distributions of sonic and Alfvenic Mach numbers. Using
subgrid one-dimensional models of MHD shocks we estimate that ~0.03 % of the
volume of a typical molecular cloud in the Milky Way will be shock heated above
50 K, at any time during the lifetime of the cloud. We discuss the impact of
this shock heating on the dynamical evolution of molecular clouds.
