Turbulent Mixing in the Interstellar Medium — an application for Lagrangian Tracer Particles

We use 3-dimensional numerical simulations of self-gravitating compressible turbulent gas in combination with Lagrangian tracer particles to investigate the mixing process of molecular hydrogen (H2) 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 10ρ0, where ρ0 denotes the mean density. Following their trajectories and using probability distribution functions, we find an upper limit for the mixing timescale of H2, which is of order 0.3Myr. This is significantly smaller than the lifetime of molecular clouds, which demonstrates the importance of the turbulent mixing of H2 as a preliminary stage to star formation. PACS numbers: 47.27.E-, 94.05.Lk, 98.38.-j Submitted to: Phys. Scr. (Conference Proceedings for ”Turbulent Mixing and Beyond 2007”)