Recent developments in planet migration theory

TL;DR

This paper reviews recent advances in planet migration theory, focusing on tidal torques, their components, and the effects of various processes on planetary drift within protoplanetary discs, including different migration types.

Contribution

It provides a comprehensive overview of the latest research on tidal torque components and their roles in different planet migration regimes, highlighting new insights into corotation torque saturation and gap-opening effects.

Findings

Enhanced understanding of corotation torque contributions.

Insights into gap-opening effects on giant planet migration.

Identification of processes affecting torque saturation.

Abstract

Planetary migration is the process by which a forming planet undergoes a drift of its semi-major axis caused by the tidal interaction with its parent protoplanetary disc. One of the key quantities to assess the migration of embedded planets is the tidal torque between the disc and planet, which has two components: the Lindblad torque and the corotation torque. We review the latest results on both torque components for planets on circular orbits, with a special emphasis on the various processes that give rise to additional, large components of the corotation torque, and those contributing to the saturation of this torque. These additional components of the corotation torque could help address the shortcomings that have recently been exposed by models of planet population syntheses. We also review recent results concerning the migration of giant planets that carve gaps in the disc (type II migration) and the migration of sub-giant planets that open partial gaps in massive discs (type III migration).