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

TL;DR

This study uses 3D simulations with Lagrangian tracers to estimate the mixing timescale of molecular hydrogen in turbulent interstellar clouds, highlighting its role in star formation.

Contribution

It introduces a novel application of tracer particles in 3D simulations to quantify H2 mixing timescales in turbulent interstellar environments.

Findings

H2 mixing timescale is approximately 0.3 Myr.

Turbulent mixing occurs faster than molecular cloud lifetimes.

Mixing is a crucial early step in star formation processes.

Abstract

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 ten times 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 0.3 Myr. 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.