The fate of close-in planets: tidal or magnetic migration?

TL;DR

This paper compares magnetic and tidal interactions affecting close-in planets, showing that both can significantly influence planetary migration timescales and must be considered in evolutionary models.

Contribution

It systematically evaluates the relative strength of magnetic and tidal torques across different star-planet systems using advanced scaling laws.

Findings

Tidal or magnetic effects can dominate depending on system characteristics.

Migration timescales can be as short as 10-100 thousand years.

Both effects are crucial for accurate modeling of planetary system evolution.

Abstract

Planets in close-in orbits interact magnetically and tidally with their host stars. These interactions lead to a net torque that makes close-in planets migrate inward or outward depending on their orbital distance. We compare systematically the strength of magnetic and tidal torques for typical observed star-planet systems (T-Tauri & hot Jupiter, M dwarf & Earth-like planet, K star & hot Jupiter) based on state-of-the-art scaling-laws. We find that depending on the characteristics of the system, tidal or magnetic effects can dominate. For very close-in planets, we find that both torques can make a planet migrate on a timescale as small as 10 to 100 thousands of years. Both effects thus have to be taken into account when predicting the evolution of compact systems.