2006/12/19 by N. Turner, N. J. Turner, T. Sano +2 · 3 citations
Physics and Astronomy · #Advanced Chemical Physics Studies #Astrophysics #Astrophysics and Star Formation Studies #Atomic and Molecular Physics #Instability #Ionization #Magnetic field #Magnetohydrodynamics #Mechanics #Physics #Shearing (physics) #Stratification (seeds) #Thermodynamics #Turbulence #astro-ph
paper · pdf · doi:10.1086/512007
published as Astrophys.J.659:729-737,2007 · to appear in the Astrophysical Journal; 25 pages, 10 figures
arxiv created 2006/12/19 · openalex publication_date 2007/04/06 · arxiv updated 2011/02/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We investigate the conditions for the presence of a magnetically inactive dead zone in protostellar disks using three-dimensional shearing-box MHD calculations, including vertical stratification, ohmic resistivity, and time-dependent ionization chemistry. Activity driven by the magneto-rotational instability fills the whole thickness of the disk at 5 AU, provided cosmic-ray ionization is present, small grains are absent, and the gas-phase metal abundance is sufficiently high. At 1 AU, the larger column density of 1700 g cm -2 means the midplane is shielded from ionizing particles and remains magneto-rotationally stable, even under the most favorable conditions considered. Nevertheless, the dead zone is effectively eliminated. Turbulence mixes free charges into the interior as they recombine, leading to a slight coupling of the midplane gas to the magnetic fields. Weak, large-scale radial fields diffuse to the midplane, where they are sheared out to produce stronger azimuthal fields. On average, the resulting midplane accretion stresses are just a few times less than in the surface layers.