Magma Ocean Waves and Thermal Variability on Lava Worlds

TL;DR

This paper explores how tidal forces induce deep magma oceans and variable thermal patterns on lava worlds, affecting their heat distribution and observable light curves.

Contribution

It models the multi-modal tidal response of magma oceans and demonstrates how orbital eccentricity causes irregular, time-variable thermal features on lava planets.

Findings

Tidal eccentricity can generate deep magma oceans on lava worlds.

Wave interference leads to irregular, shifting hotspots and variable thermal light curves.

Tidal heating can cause entire mantles of Earth-sized planets to become tidally liquefied.

Abstract

Lava worlds are rocky planets with dayside skins made molten by stellar irradiation. Tidal heating on these shortest-period planets is more than skin deep. We show how orbital eccentricities of just a few percent (within current observed bounds and maintained secularly by exterior companions) can create deep magma oceans. ``Lava tidal waves'' slosh across these oceans; we compute the multi-modal response of the ocean to tidal forcing, subject to a coastline at the day-night terminator and a parameterized viscous drag. Wave interference produces a dayside heat map that is spatially irregular and highly time-variable; hotspots can wander both east and west of the substellar point, and thermal light curves can vary and spike aperiodically, from orbit to orbit and within an orbit. Heat deposited by tides is removed in steady state by a combination of fluid, mushy, and solid-state convection in the mantle. For Earth-sized planets with sub-day periods, the entire mantle may be tidally liquified.