Characterizing the structure of interstellar turbulence

Original · EN

Modeling the structure of molecular clouds depends on good methods to statistically compare simulations with observations in order to constrain the models. Here we characterize a suite of hydrodynamical and magnetohydrodynamical (MHD) simulations of supersonic turbulence using an averaged wavelet transform, the Delta-variance, that has been successfully used to characterize observations. We find that, independent of numerical resolution and dissipation, the only models that produce scale-free, power-law Delta-variance spectra are those with hypersonic Mach numbers above M 4, while slower supersonic turbulence tends to show characteristic scales and produce non-power-law spectra. Magnetic fields have only a minor influence on this tendency, though they tend to reduce the scale-free nature of the turbulence, and increase the transfer of energy from large to small scales. The evolution of the characteristic length scale seen in supersonic turbulence follows exactly the t¹/² power-law predicted from recent studies of the kinetic energy decay rate.