Dynamics Near the Inner Dead-Zone Edges in a Proprotoplanetary Disk
arxiv(2024)
摘要
We perform three-dimensional global non-ideal magnetohydrodynamic simulations
of a protoplanetary disk containing the inner dead-zone edge. We take into
account realistic diffusion coefficients of the Ohmic resistivity and ambipolar
diffusion based on detailed chemical reactions with a single-size dust grains.
We found that the conventional dead zone identified by the Elsässer numbers
of the Ohmic resistivity and ambipolar diffusion is divided into two regions:
"the transition zone" and "the coherent zone". The coherent zone has the same
properties as the conventional dead zone, and extends outside of the transition
zone in the radial direction. Between the active and coherent zones, we
discover the transition zone whose inner edge is identical to that of the
conventional dead-zone. The transition zone extends out over the regions where
thermal ionization determines diffusion coefficients. The transition zone has
completely different physical properties than the conventional dead zone, the
so-called undead zone, and zombie zone. Combination of amplification of the
radial magnetic field owing to the ambipolar diffusion and a steep radial
gradient of the Ohmic diffusivity causes the efficient evacuation of the net
vertical magnetic flux from the transition zone within several rotations.
Surface gas accretion occurs in the coherent zone but not in the transition
zone. The presence of the transition zone prohibits mass and magnetic flux
transport from the coherent zone to the active zone. Mass accumulation occurs
at both edges of the transition zone as a result of mass supply from the active
and coherent zones.
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