On shocks driven by high-mass planets in radiatively inefficient disks. II. Three-dimensional global disk simulations

TL;DR

This study uses three-dimensional simulations to show that high-mass planets can generate shock heating and turbulence in protoplanetary disks, potentially explaining observed spiral features with high temperatures and large pitch angles.

Contribution

It extends previous two-dimensional models to three dimensions, demonstrating shock-induced heating, turbulence, and convection caused by high-mass planets in protoplanetary disks.

Findings

Shocks heat the disk gas to temperatures much higher than ambient.

Shock bores and turbulence form around Lindblad resonances.

Regions heated by shocks can become superadiabatic, leading to convection.

Abstract

Recent high-resolution, near-infrared images of protoplanetary disks have shown that these disks often present spiral features. Spiral arms are among the structures predicted decades ago by numerical simulations of disk-planet interaction and thus it is tempting to suspect that planetary perturbers are responsible for the observed signatures. However, such interpretation is not free of problems. The spirals are found to have large pitch angles, and in at least one case (HD 100546) the spiral feature appears effectively unpolarized, which implies thermal emission of the order of 1000K (465$\pm$40K at closer inspection). We have recently shown in two-dimensional models that shock dissipation in the supersonic wake of high-mass planets can lead to significant heating if the disk is sufficiently adiabatic. In this paper we extend this analysis to three dimensions in thermodynamically evolving disks. We use the Pencil Code in spherical coordinates for our models, with a prescription for thermal cooling based on the optical depth of the local vertical gas column. We use a 5$M_J$ planet, and show that shocks in the region around the planet where the Lindblad resonances occur heat the gas to substantially higher temperatures than the ambient disk gas at that radius. The gas is accelerated vertically away from the midplane by the shocks to form shock bores, and the gas falling back toward the midplane breaks up into a turbulent surf near the Lindblad resonances. This turbulence, although localized, has high $\alpha$ values, reaching 0.05 in the inner Lindblad resonance, and 0.1 in the outer one. We also find evidence that the disk regions heated up by the planetary shocks eventually becomes superadiabatic, generating convection far from the planet's orbit.