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Turbulent Mixing and the Dead Zone in Protostellar Disks
- Source :
- ResearcherID
- Publication Year :
- 2006
-
Abstract
- We investigate the conditions for the presence of a magnetically inactive dead zone in protostellar disks, using 3-D shearing-box MHD calculations including vertical stratification, Ohmic resistivity and time-dependent ionization chemistry. Activity driven by the magnetorotational 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 magnetorotationally 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. The resulting midplane accretion stresses are just a few times less than in the surface layers on average.<br />to appear in the Astrophysical Journal; 25 pages, 10 figures
- Subjects :
- Physics
Turbulence
Astrophysics (astro-ph)
Stratification (water)
FOS: Physical sciences
Astronomy and Astrophysics
Cosmic ray
Astrophysics
Molecular physics
Magnetic field
Space and Planetary Science
Electrical resistivity and conductivity
Ionization
Magnetorotational instability
Astrophysics::Earth and Planetary Astrophysics
Magnetohydrodynamics
Astrophysics::Galaxy Astrophysics
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- ResearcherID
- Accession number :
- edsair.doi.dedup.....5bfa8bddd4086f21dc1b911833e4fb66