Kinetic energy decay rates of supersonic and super-Alfvenic turbulence in star-forming clouds

We compute 3D models of supersonic, sub-Alfvenic, and super-Alfvenic decaying turbulence, with an isothermal equation of state appropriate for star-forming interstellar clouds of molecular gas. We find that in 3D the kinetic energy decays as t(-eta), with 0.85 < eta < 1.2. In 1D magnetized turbulence actually decays faster than unmagnetized turbulence. We compared different algorithms, and performed resolution studies reaching 256(3) zones or 70(3) particles. External driving must produce the observed long lifetimes and supersonic motions in molecular clouds, as undriven turbulence decays too fast.