Self-organization in Turbulent Molecular Clouds: Compressional versus Solenoidal Modes

We use three-dimensional numerical simulations to study self-organization in supersonic turbulence in molecular clouds. Our numerical experiments describe decaying and driven turbulent flows with an isothermal equation of state, sonic Mach numbers from 2 to 10, and various degrees of magnetization. We focus on properties of the velocity field and, specifically, on the level of its potential (dilatational) component as a function of turbulent Mach number, magnetic field strength, and scale. We show how extreme choices of either purely solenoidal or purely potential forcing can reduce the extent of the inertial range in the context of periodic box models for molecular cloud turbulence. We suggest an optimized forcing to maximize the effective Reynolds number in numerical models.