Turbulent mixing in the interstellar medium: an application for Lagrangian tracer particles

We use three-dimensional numerical simulations of self-gravitating compressible turbulent gas in combination with Lagrangian tracer particles to investigate the mixing process of molecular hydrogen (H-2) in interstellar clouds. Tracer particles are used to represent shock-compressed dense gas, which is associated with H2. We deposit tracer particles in regions of density contrast in excess of 10 rho(0), where rho(0) denotes the mean density. Following their trajectories and using probability distribution functions, we find an upper limit for the mixing timescale of H-2, which is of the order of 0.3 Myr. This is significantly smaller than the lifetime of molecular clouds, which demonstrates the importance of the turbulent mixing of H-2 as a preliminary stage to star formation.