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Abstract: Planets form inside protostellar disks in a dead zone where the electricalresistivity of the gas is too high for magnetic forces to drive turbulence. Weshow that much of the dead zone nevertheless is active and flows toward thestar while smooth, large-scale magnetic fields transfer the orbital angularmomentum radially outward. Stellar X-ray and radionuclide ionization sustain aweak coupling of the dead zone gas to the magnetic fields, despite the rapidrecombination of free charges on dust grains. Net radial magnetic fields aregenerated in the magneto-rotational turbulence in the electrically conductingtop and bottom surface layers of the disk, and reach the midplane by Ohmicdiffusion. A toroidal component to the fields is produced near the midplane bythe orbital shear. The process is similar to the magnetization of the Solartachocline. The result is a laminar, magnetically-driven accretion flow in theregion where the planets form.

Autor: N. J. Turner, T. Sano


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