3D Radiation Non-ideal Magnetohydrodynamical Simulations Of The Inner Rim In Protoplanetary Disks

TL;DR

This study uses advanced 3D radiation non-ideal MHD simulations to explore the inner regions of protoplanetary disks, revealing turbulence, vortex formation, and variable infrared flux near the silicate sublimation front.

Contribution

First global 3D radiation non-ideal MHD simulations of the inner protoplanetary disk with detailed physics including starlight heating and dust sublimation.

Findings

Magnetorotational turbulence exists near the sublimation front at 0.5 AU.

A vortex forms at the dead zone's inner edge, affecting disk structure.

Near-infrared flux varies several percent monthly, influenced by the vortex.

Abstract

Many planets orbit within an AU of their stars, raising questions about their origins. Particularly puzzling are the planets found near the silicate sublimation front. We investigate conditions near the front in the protostellar disk around a young intermediate-mass star, using the first global 3-D radiation non-ideal MHD simulations in this context. We treat the starlight heating; the silicate grains sublimation and deposition at the local, time-varying temperature and density; temperature-dependent Ohmic dissipation; and various initial magnetic fields. The results show magnetorotational turbulence around the sublimation front at 0.5 AU. The disk interior to 0.8 AU is turbulent, with velocities exceeding 10% of the sound speed. Beyond 0.8 AU is the dead zone, cooler than 1000 K and with turbulence orders of magnitude weaker. A local pressure maximum just inside the dead zone concentrates solid particles, favoring their growth. Over many orbits, a vortex develops at the dead zones inner edge, increasing the disks thickness locally by around 10%. We synthetically observe the results using Monte Carlo transfer calculations, finding the sublimation front is near-infrared bright. The models with net vertical magnetic fields develop extended, magnetically-supported atmospheres that reprocess extra starlight, raising the near-infrared flux 20%.The vortex throws a nonaxisymmetric shadow on the outer disk. At wavelengths > 2 micron, the flux varies several percent on monthly timescales. The variations are more regular when the vortex is present. The vortex is directly visible as an arc at ultraviolet through near-infrared wavelengths, given sub-AU spatial resolution.