2002/05/17 by A. Lazarian, Lazarian, A., Huirong Yan +1
Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0205283
16 pages, 3 figures, "Best of Science", submitted
arxiv created 2002/05/17 · openalex publication_date 2002/05/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However, earlier treatments disregarded magnetic field and used Kolmogorov turbulence. Unlike hydro turbulence, MHD turbulence is anisotropic on small scales. Moreover, compressible modes are important for MHD and magnetic perturbations can directly interact with grains. We provide calculations of grain relative motion for realistic interstellar turbulence driving that is consistent with the velocity dispersions observed in diffuse gas and for realistic grain charging. We account for the turbulence cutoff arising from abmipolar drag. Our results on grain shattering are consistent with the customary accepted cutoff size. We obtain grain velocities for turbulence with parameters consistent with those in HI and dark clouds. These velocities are smaller than those in earlier papers, where MHD effects were disregarded. Finally, we consider grain velocities arising from photoelectric emission, radiation pressure and the thrust due to molecular hydrogen formation. These are lower than relative velocities induced by turbulence. We conclude that turbulence should prevent these mechanisms from segregating grains by size.