We present numerical studies of compressible , decaying turbulence , with and without magnetic fields , with initial rms Alfvén and Mach numbers ranging up to five , and apply the results to the question of the support of star-forming interstellar clouds of molecular gas .
We find that , in 1D , magnetized turbulence actually decays faster than unmagnetized turbulence .
In all the regimes that we have studied 3D turbulence—super-Alfvénic , supersonic , sub-Alfvénic , and subsonic—the kinetic energy decays as ( t - t _ { 0 } ) ^ { - \eta } , with 0.85 < \eta < 1.2 .
We compared results from two entirely different algorithms in the unmagnetized case , and have performed extensive resolution studies in all cases , reaching resolutions of 256 ^ { 3 } zones or 350,000 particles .
We conclude that the observed long lifetimes and supersonic motions in molecular clouds must be due to external driving , as undriven turbulence decays far too fast to explain the observations .