Migrating Low-Mass Planets in Inviscid Dusty Protoplanetary Discs

TL;DR

This study uses high-resolution simulations to show that dust-rich protoplanetary discs can slow, halt, or reverse the inward migration of low-mass planets through dust-induced effects and stochastic interactions.

Contribution

It introduces a new understanding of planet migration in dusty environments, highlighting the role of dust dynamics and vortices in altering migration paths.

Findings

Dust can slow down or reverse planet migration.

Stochastic migration occurs with high dust-to-gas ratios.

Dust vortices scatter planets, affecting their orbital evolution.

Abstract

Disc-driven planet migration is integral to the formation of planetary systems. In standard, gas-dominated protoplanetary discs, low-mass planets or planetary cores undergo rapid inwards migration and are lost to the central star. However, several recent studies indicate that the solid component in protoplanetary discs can have a significant dynamical effect on disc-planet interaction, especially when the solid-to-gas mass ratio approaches unity or larger and the dust-on-gas drag forces become significant. As there are several ways to raise the solid abundance in protoplanetary discs, for example through disc winds and dust-trapping in pressure bumps, it is important to understand how planets migrate through a dusty environment. To this end, we study planet migration in dust-rich discs via a systematic set of high-resolution, two-dimensional numerical simulations. We show that the inwards migration of low-mass planets can be slowed down by dusty dynamical corotation torques. We also identify a new regime of stochastic migration applicable to discs with dust-to-gas mass ratios $\gtrsim 0.3$ and particle Stokes numbers $\gtrsim 0.03$. In these cases, disc-planet interaction leads to the continuous development of small-scale, intense dust vortices that scatter the planet, which can potentially halt or even reverse the inwards planet migration. We briefly discuss the observational implications of our results and highlight directions for future work.