Michael D. Smith
Astronomisches Institut der Universität
Physical Review Letters, 1998, 80, 2754
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 tx, with 0.85 < x < 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 2563 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.
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MPI Astronomie theory group