Decay Timescales of MHD Turbulence inMolecular

We compute 3D models of supersonic, sub-Alfv enic, and super-Alfv enic decaying turbulence, with initial rms Alfv en and Mach numbers ranging up to ve, and an isothermal equation of state appropriate for star-forming interstellar clouds of molecular gas. We nd that in 3D the kinetic energy decays as t ? , with 0:85 < < 1:2. In 1D magnetized turbulence actually decays faster than unmagnetized turbulence. We compared diierent 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.