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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358545.0, MPI für Astronomie / Publikationen_mpia
Turbulent mixing and the dead zone in protostellar disks
Authors:Turner, N. J.; Sano, T.; Dziourkevitch, N.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:729
End Page:737
Audience:Not Specified
Abstract / Description: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.
Free Keywords:Stars: Circumstellar Matter; Instabilities; Magnetohydrodynamics: MHD; Solar System: Formation; Stars: Formation
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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