Thaddeus Komacek

Abstract:

Introduction: Recent advances in observation with the JWST and high-resolution ground-based instruments have enabled the study of exoplanets to progress towards atmospheric characterisation, as opposed to merely detection. Hot and ultra-hot Jupiters remain among the best characterised and studied class of exoplanet, due to their large sizes and close orbits, however how the internal heating and resulting radius inflation of bloated ultra-hot Jupiters and related coupling to the internal magnetic field impacts their atmospheric circulation remains an open question. Moreover, the impact of atmospheric dynamics on observable properties can now be studied in detail. This study investigates the effect of varying both atmospheric drag and internal heat flux on the observable properties of WASP-76b, with comparisons made to JWST NIRSpec white-light phase curves. In addition, we perform a broader parameter sweep using the SPARC/MITgcm to investigate the influence of internal heating and inflated radii on the observable properties of hot and ultra-hot Jupiters.Methods: A suite of general circulation models are run, which solve the primitive equations of meteorology coupled to non-grey correlated-k radiative transfer with the SPARC/MITgcm [1]. The effect of Lorentz forces is represented by changing a spatially constant drag timescale , and for WASP-76b we consider two different internal heat fluxes for comparison, across the range of predicted values for hot and ultra-hot Jupiters [2]. We then will perform a broader parameter sweep, exploring the space of inflated-radii hot and ultra-hot Jupiters by covering a range of irradiation levels from zero-albedo full-redistribution equilibrium temperatures of 1000 – 3200K, again using the SPARC/MITgcm. This parameter space is inclusive of most inflated gas-giant planets, excluding KELT-9b, and will allow us to study the impact of internal heating on atmospheric circulation, with interior heating and evolution modelled using MESA [3]. We then use the gCMCRT radiative transfer code [4] to post-process the GCM results to produce simulated phase curves.Results: The key result from this study is shown in Figure 1, with simulated phase curves shown in comparison to Spitzer telescope data [5] at 3.6mm. We make the comparison to Spitzer data here as a placeholder for the comparison to JWST NIRSpec data, as the JWST data is not yet published. Figure 3 shows the impact of the interior heat flux on the internal temperature structure of WASP-76b. There is no observable difference between the interior heat flux scenarios. Figures 2 and 4 show characteristics of the atmospheric dynamics and temperature structure. Strong drag acts to suppress all winds throughout the atmosphere, as is expected, while intermediate drag removes the offset of the hot spot due to the suppression of the deep equatorial jet. There is a strong equatorial jet within the deep atmosphere, and the T-P profile implies that cloud species Al2O4 and Mg2SiO4 can form on the night-side and terminators of WASP-76b, and within its deep atmosphere.Conclusions: Spitzer data is best matched by a strong () drag case. There is no potentially observable difference between the hot interior flux and cold interior flux. The comparisons of these simulated phase curve to JWST NIRSpec white-light phase curves will help further constrain drag in the ultra-hot regime, which will be a useful point of comparison to other ultra-hot Jupiters. Other ultra-hot Jupiters with Spitzer phase-curves (WASP-18b [6], WASP-103b [7], WASP-121b [8]) also show high dayside-nightside temperature differences. This may imply that the drag mechanisms are similar in each planet in the ultra-hot regime (~2000-2500 K). New JWST NIRSpec/G395H phase-curve data (JWST GO proposal 5268) will also constrain metallicity, breaking the drag/metallicity degeneracy. The similarity in deep-atmosphere temperature shown by Figure 3 motivates the need for a parameter sweep where the temperature at the bottom boundary is varied, as opposed to an interior heat flux, in order to speed up convergence. Likewise, the T-P profile in Figure 4 motivates the need for longer simulation runs, as the model has not reached equilibrium within the deep atmosphere.References:[1] Showman, A.P. et al. (2009), The Astrophysical Journal, 699(1), pp. 564–584.[2] Thorngren, D. et al. (2019), ApJL (Vol. 884, Issue 1)[3] Jermyn, A.S. et al. (2023), The Astrophysical Journal Supplement Series, 265, p. 15.[4] Lee, E.K. et al. (2022), The Astrophysical Journal, 929(2), p. 180[5] May, E.M. et al. (2021), The Astronomical Journal, 162(4), p. 158.[6] Maxted, P.F. et al. (2012), Monthly Notices of the Royal Astronomical Society, 428(3), pp. 2645–2660[7] Kreidberg, L. et al. (2018), The Astronomical Journal, 156(1), p. 17[8] Davenport, B. et al. (2025),  Available at: https://arxiv.org/abs/2503.12521 (Accessed: 20 March 2025).

Abstract:

Clouds have broad significance in understanding the evolution and climate of planetary atmospheres. Moreover, the presence of clouds in the atmospheres of hot Jupiter exoplanets is supported both by direct spectral detections (Grant et al. 2023, Inglis et al. 2024), and observational trends, such as nightside brightness temperature (Beatty et al. 2019) and phase curve hot spot offsets (Bell et al. 2024), suggesting that an accurate understanding of clouds is needed, not only to understand the atmospheres of these planets, but to properly interpret observations. However, the properties of clouds are impacted by inherently coupled effects of circulation, radiation, and cloud microphysics. Full coupling of these processes remains computationally expensive, and as a result, current modeling schemes implement simplified cloud parametrizations that neglect one or more of these effects. Within this work, we implement a one-way indirect coupling of the cloud microphysical model 1D CARMA and MITgcm/DISORT, a general circulation model including double-grey radiative transfer, through including a novel particle size distribution that better represents the output of CARMA. We use pre-existing CARMA data for ultra-hot Jupiter TOI-1431b from Gao & Powell (2021), which has particle size distributions that are not well described by a log-normal distribution, with corundum in particular displaying distinctly bimodal behavior. We hypothesize the smaller particle size mode corresponds to nucleation, whereas the larger particle size has formed through condensational growth and coagulation. We present a particle size distribution function that can account for this wide range of distribution variability using two log-normals and two log-exponentials. We implement this particle size distribution for corundum within MITgcm/DISORT for ultra-hot Jupiter TOI-1431b, and compare this work to that of Komacek et al. (2022a), which includes a log-normal roughly corresponding with the larger particle size mode in our distribution. We present the results of this comparison, and discuss the impact of particle size distribution on properties of ultra-hot Jupiters.

Abstract:

Hot and ultra-hot Jupiters are currently the best observational targets to study the effects of clouds on exoplanet atmospheres. Observations have reported westward optical phase curve offsets, weak spectral features, and nightside temperatures remaining constant with increasing stellar flux, which may together be explained by the presence of exoplanetary clouds. Although there are many models that simulate the 3D structure and circulation of hot/ultra-hot Jupiters and many microphysical models describing the formation of clouds, very few models exist that couple these two approaches. This gap, along with recent JWST observations unmatched by models, suggests a need for more accurate models to track the formation of clouds as well as their radiative feedback on atmospheric circulation and dynamics. In this work, we couple two models to better understand how atmospheric dynamics and cloud microphysics in hot Jupiter atmospheres affect each other and the observable properties of such planets in the context of JWST data. We run cloudless 3D general circulation model (GCM) simulations using the SPARC/MITgcm for WASP-43b and WASP-121b, two hot/ultra-hot Jupiters that already have high-quality data from HST and recent JWST observations. We then feed the temperature-pressure profile outputs from the GCM simulations into 1D CARMA, which models the microphysics of mineral clouds in hot and ultra-hot Jupiter atmospheres. Finally, we use our coupled circulation and cloud formation results to calculate synthetic spectra with a ray-striking radiative transfer code and compare our results to emission and transmission observations of WASP-43b and WASP-121b. We find that various cloud species, including corundum, forsterite, and iron, form everywhere on WASP-43b and on the nightside and west limb of WASP-121b, perhaps explaining the most recent phase curve observations of these planets. We discuss implications for the interpretation of JWST/MIRI and JWST/NIRSpec observations of WASP-43b and WASP-121b respectively, with implications for the broader planetary population.

Abstract:

Recent JWST transmission and emission spectroscopic observation of hot Jupiters have demonstrated that mineral clouds are likely common in hot Jupiter atmospheres. These mineral clouds have long been predicted to form and persist on the nightside and western dayside of hot Jupiters by cloud microphysical models and 3D General Circulation Models. Given the capability of JWST and recent advancements in modeling techniques, the time is right to determine the prevalence and distribution of mineral clouds across the parameter regime of hot Jupiters in order to provide a detailed test of our theoretical understanding of cloud nucleation, transport and growth processes, and the radiative feedback of clouds on the atmospheric circulation and climate of hot Jupiters. In this work, we develop an indirectly coupled cloud microphysics and atmospheric dynamics framework in order to present theoretical expectations for the 3D distribution of mineral clouds across hot Jupiter planetary parameter space. To do so, we develop a fundamental understanding of the cloud speciation alongside particle size and spatial distribution by feeding the results of 3D cloud-free GCMs into 1D CARMA cloud microphysics simulations. We then use these results to drive 3D MITgcm simulations of hot Jupiters with cloud-radiative feedback. We use a grid of GCM simulations to assess the radiative impact on clouds of the climates of hot and ultra-hot Jupiters. Notably, we find that mineral cloud particle size distributions are not ubiquitously unimodal and log-normal, leading to potentially stark differences between the 3D cloud distributions in our work compared to previous work that assumed a single log-normal cloud particle size distribution. Finally, we will discuss paths forward toward coupling the cloud microphysics and atmospheric dynamics of hot Jupiters using a modeling hierarchy encompassing multi-dimensional cloud microphysics and atmospheric dynamics.