Dead Zone Accretion Flows in Protostellar Disks

Abstract

Planets form inside protostellar disks in a dead zone where the electrical resistivity of the gas is too high for magnetic forces to drive turbulence. We show that much of the dead zone nevertheless is active and flows toward the star while smooth, large-scale magnetic fields transfer the orbital angular momentum radially outward. Stellar X-ray and radionuclide ionization sustain a weak coupling of the dead zone gas to the magnetic fields, despite the rapid recombination of free charges on dust grains. Net radial magnetic fields are generated in the magneto-rotational turbulence in the electrically conducting top and bottom surface layers of the disk, and reach the midplane by Ohmic diffusion. A toroidal component to the fields is produced near the midplane by the orbital shear. The process is similar to the magnetization of the Solar tachocline. The result is a laminar, magnetically-driven accretion flow in the region where the planets form.

12 pages, 4 figures

References in corpus (3)

• Grain Retention and Formation of Planetesimals near the Snow Line in MRI-driven Turbulent Protoplanetary Disks
• Magnetic fields in protoplanetary disks
• Dust Coagulation and Settling in Layered Protoplanetary Disks

Cited by in corpus (7)

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• Formation of Water in the Warm Atmospheres of Protoplanetary Disks
• Two-Dimensional Transport of Solids in Viscous Protoplanetary Disks
• New composite models of partially ionized protoplanetary disks