Local Linear Analysis of Interaction between a Planet and Viscous Disk and an Implication on Type I Planetary Migration

TL;DR

This study analyzes how viscosity influences disk-planet interactions and modifies type I planetary migration, revealing that viscous effects significantly alter the local density structure and torque calculations near the planet.

Contribution

It provides a detailed linear analysis of viscous disk effects on planet migration, highlighting the importance of local density structures and revising previous inviscid assumptions.

Findings

Density structure near the planet is altered by viscosity.

One-sided torque varies significantly with Reynolds number.

Viscous effects can qualitatively change planet-disk interactions.

Abstract

We investigate the effects of viscosity on disk-planet interaction and discuss how type I migration of planets is modified. We have performed a linear calculation using shearing-sheet approximation and obtained the detailed, high resolution density structure around the planet embedded in a viscous disk with a wide range of viscous coefficients. We use a time-dependent formalism that is useful in investigating the effects of various physical processes on disk-planet interaction. We find that the density structure in the vicinity of the planet is modified and the main contribution to the torque comes from this region, in contrast to inviscid case. Although it is not possible to derive total torque acting on the planet within the shearing-sheet approximation, the one-sided torque can be very different from the inviscid case, depending on the Reynolds number. This effect has been neglected so far but our results indicate that the interaction between a viscous disk and a planet can be qualitatively different from an inviscid case and the details of the density structure in the vicinity of the planet is critically important.