Atmospheric Circulation and Composition of GJ1214b

TL;DR

This study models GJ1214b's atmosphere with different compositions to understand how circulation patterns can reveal its atmospheric makeup, aiding the characterization of similar exoplanets.

Contribution

It presents the first comprehensive atmospheric circulation models of GJ1214b considering multiple compositions and radiative effects, linking circulation patterns to atmospheric composition.

Findings

All models show superrotating zonal winds (~1-2 km/s).

Heat advection varies significantly with composition.

Circulation differences relate to molecular weight and opacity effects.

Abstract

The exoplanet GJ1214b presents an interesting example of compositional degeneracy for low-mass planets. Its atmosphere may be composed of water, super-solar or solar metallicity material. We present atmospheric circulation models of GJ1214b for these three compositions, with explicit grey radiative transfer and an optional treatment of MHD bottom drag. All models develop strong, superrotating zonal winds (~ 1-2 km/s). The degree of eastward heat advection, which can be inferred from secondary eclipse and thermal phase curve measurements, varies greatly between the models. These differences are understood as resulting from variations in the radiative times at the thermal photosphere, caused by separate molecular weight and opacity effects. Our GJ1214b models illustrate how atmospheric circulation can be used as a probe of composition for similar tidally-locked exoplanets in the mini-Neptune/waterworld class.