Dynamic mineral clouds on HD 189733b I. 3D RHD with kinetic, non-equilibrium cloud formation

TL;DR

This paper presents a comprehensive 3D radiative-hydrodynamic model of cloud formation on the hot Jupiter exoplanet HD 189733b, incorporating kinetic microphysics, atmospheric dynamics, and cloud feedback effects to reveal complex, spatially varying cloud structures.

Contribution

It introduces a novel 3D coupled RHD and kinetic microphysical cloud formation model for exoplanet atmospheres, including cloud feedback and detailed composition.

Findings

Cloud particles are mostly sub-micron in size.

Denser clouds form near the terminator and deeper layers.

Different mineral compositions dominate at various latitudes.

Abstract

Observations of exoplanet atmospheres have revealed the presence of cloud particles in their atmospheres. 3D modelling of cloud formation in atmospheres of extrasolar planets coupled to the atmospheric dynamics has long been a challenge. We investigate the thermo-hydrodynamic properties of cloud formation processes in the atmospheres of hot Jupiter exoplanets. We simulate the dynamic atmosphere of HD 189733b with a 3D model that couples 3D radiative-hydrodynamics with a kinetic, microphysical mineral cloud formation module designed for RHD/GCM exoplanet atmosphere simulations. Our simulation includes the feedback effects of cloud advection and settling, gas phase element advection and depletion/replenishment and the radiative effects of cloud opacity. We model the cloud particles as a mix of mineral materials which change in size and composition as they travel through atmospheric thermo-chemical environments. All local cloud properties such as number density, grain size and material composition are time-dependently calculated. Gas phase element depletion as a result of cloud formation is included in the model. In-situ \textit{effective medium theory} and Mie theory is applied to calculate the wavelength dependent opacity of the cloud component. We present a 3D cloud structure of a chemically complex, gaseous atmosphere of the hot Jupiter HD 189733b. Mean cloud particle sizes are typically sub-micron (0.01-0.5 $\mu$m) at pressures less than 1 bar with hotter equatorial regions containing the smallest grains. Denser cloud structures occur near terminator regions and deeper ($\sim$ 1 bar) atmospheric layers. Silicate materials such as MgSiO$_{3}$[s] are found to be abundant at mid-high latitudes, while TiO$_{2}$[s] and SiO$_{2}$[s] dominate the equatorial regions.