Type I Planet Migration in Nearly Laminar Disks

Abstract

We describe 2D hydrodynamic simulations of the migration of low-mass planets ($\le 30M_{\oplus }$) in nearly laminar disks (viscosity parameter $\alpha <10^{-3}$) over timescales of several thousand orbit periods. We consider disk masses of 1, 2, and 5 times the minimum mass solar nebula, disk thickness parameters of $H/r=0.035$ and 0.05, and a variety of $\alpha$ values and planet masses. Disk self-gravity is fully included. Previous analytic work has suggested that Type I planet migration can be halted in disks of sufficiently low turbulent viscosity, for $\alpha \sim 10^{-4}$. The halting is due to a feedback effect of breaking density waves that results in a slight mass redistribution and consequently an increased outward torque contribution. The simulations confirm the existence of a critical mass ($M_{cr}\sim 10M_{\oplus }$) beyond which migration halts in nearly laminar disks. For $α\ga 10^{-3}$, density feedback effects are washed out and Type I migration persists. The critical masses are in good agreement with the analytic model of Rafikov (2002). In addition, for $α\la 10^{-4}$ steep density gradients produce a vortex instability, resulting in a small time-varying eccentricity in the planet's orbit and a slight outward migration. Migration in nearly laminar disks may be sufficiently slow to reconcile the timescales of migration theory with those of giant planet formation in the core accretion model.

3 figures, accepted to ApJL

References in corpus (2)

• Cavity opening by a giant planet in a protoplanetary disc and effects on planetary migration
• Evolution of Migrating Planets Undergoing Gas Accretion