Effects of Radiative Diffusion on the Dynamical Corotation Torque in Three-Dimensional Protoplanetary Disks

For migrating low-mass planets, the deformation of the horseshoe orbits along with the vortensity gradient in the background disk creates an additional torque known as the dynamical corotation torque. Previous studies predicted that the dynamical corotation torque in two-dimensional (2D) disks is positive for an inwardly-migrating planet. However, a recent study showed that buoyancy resonance in three-dimensional (3D) adiabatic disks enhances the vortensity inside the corotation region, making the dynamical corotation torque negative. In this work, we run 3D simulations of radiative 3D disks and show that radiative diffusion suppresses the buoyancy resonance and makes the dynamical corotation torque positive. Our results suggest various thermodynamic processes including radiative diffusion, stellar irradiation, and accretion heating may have important consequences on migration of low-mass planets.