Dynamics Near the Inner Dead-Zone Edges in a Proprotoplanetary Disk

TL;DR

This study uses advanced 3D non-ideal MHD simulations to reveal complex magnetic and flow structures near the inner dead-zone edge in protoplanetary disks, highlighting a transition zone with distinct properties affecting accretion.

Contribution

It introduces a detailed simulation-based analysis of the inner dead-zone edge, identifying a new transition zone with unique physical properties and magnetic flux behavior.

Findings

The dead zone splits into transition and coherent zones with different properties.

The transition zone inhibits mass and magnetic flux transport between zones.

Mass accumulates at the edges of the transition zone due to supply from adjacent zones.

Abstract

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 single-size dust grains. We found that the conventional dead zone identified by the Els\"asser 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, the inner edge of which 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 the zombie zone. The 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.