# Gravito-turbulence in irradiated protoplanetary discs

## TL;DR

This study uses radiation hydrodynamics simulations to investigate gravito-turbulence in irradiated protoplanetary discs at 50 AU, revealing a finite surface density range for turbulence, the nature of turbulent motions, and the effects of irradiation and cooling.

## Contribution

First detailed simulation study of gravito-turbulence in irradiated protoplanetary discs with realistic physics, identifying the turbulence range and energy transport mechanisms.

## Key findings

- Gravito-turbulence exists between 80 and 250 gcm$^{-2}$ surface density.
- Turbulent motions are supersonic at all heights, dissipating via shocks and compression.
- Irradiation has minimal impact on midplane turbulence unless the grazing angle exceeds 0.32.

## Abstract

Using radiation hydrodynamics simulations in a local stratified shearing box with realistic equations of state and opacities, we explored the outcome of self-gravity at 50 AU in a protoplanetary disc irradiated by the central star. We found that gravito-turbulence is sustained for a finite range of the surface density, from $\sim 80$ to $\sim$ 250 gcm$^{-2}$. The disk is laminar below the range while fragments above it. In the range of gravito-turbulence, the Toomre parameter decreases monotonically from $\sim 1$ to $\sim 0.7$ as the surface density increases while an effective cooling time is almost constant at $\sim 4$ in terms of the inverse of the orbital frequency. The turbulent motions are supersonic at all heights, which dissipates through both shock waves and compressional heating. The compressional motions, occurring near the midplane, create upward flows, which not only contribute to supporting the disc but also to transporting the dissipated energy to the disc surfaces. The irradiation does not affect much the gravito-turbulence near the midplane unless the grazing angle is larger than 0.32. We also show that a simple cooling function with a constant cooling time does not approximate the realistic cooling.