OUTFLOW-DRIVEN TURBULENCE IN MOLECULAR CLOUDS

In this paper, we explore the relationship between protostellar outflows and turbulence in molecular clouds. Using three-dimensional numerical simulations we focus on the hydrodynamics of multiple outflows interacting within a parsec scale volume. We explore the extent to which transient outflows injecting directed energy and momentum into a subvolume of a molecular cloud can be converted into random turbulent motions. We show that turbulence can readily be sustained by these interactions and it is possible to broadly characterize an effective driving scale of the outflows. We compare the velocity spectrum obtained in our studies with that of isotropically forced hydrodynamic turbulence finding that in outflow-driven turbulence a power law of the form E(k) proportional to k(-beta) is indeed achieved. However, we find that a steeper spectrum beta similar to 2.74 is obtained in outflow-driven turbulence models than in isotropically forced simulations beta similar to 2.45. We discuss possible physical mechanisms responsible for these results as well as their implications for turbulence in molecular clouds where outflows will act in concert with other processes such as gravitational collapse.