Thaddeus Komacek

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.

Abstract:

Space weather events in exoplanetary environments sourced from transient host star emissions, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence a planet's habitability and atmospheric evolution history. These time-dependent events may also affect our ability to measure and interpret its properties by modulating reservoirs of key chemical compounds and changing the atmosphere’s brightness temperature. The majority of previous work focusing on photochemical effects, ground-level UV dosages, and consequences on observed spectra. Here, using three-dimensional general circulation models with interactive photochemistry, we simulate the climate and chemical impacts of stellar energetic particle events and periodic enhancements of UV photons. We use statistical methods to examine their effects on synchronously rotating TRAPPIST-1e-like planets on a range of spatiotemporal scales. We find that abrupt thermospheric cooling is associated with radiative cooling of NO and CO2, and middle-to-lower atmospheric warming is associated with elevated infrared absorbers such as N2O and H2O. In certain regimes, in particular for climates around moderately active stars, atmospheric temperature changes are strongly affected by O3 variability. Cumulative effects are largely determined by the flare frequency and the instantaneous effects are dependent on the flare’s spectral shape and energy. In addition to effects on planetary climate and atmospheric chemistry, we find that intense flares can energize the middle atmosphere, causing enhancements in wind velocities up to 40 m s−1 in substellar nightsides between 30 and 50 km in altitude. Our results suggest that successive, more energetic eruptive events from younger stars may be a pivotal factor in determining the atmosphere dynamics of their planets.

Abstract:

Sub-Neptunes, the most common planet type, remain poorly understood. Their atmospheres are expected to be diverse, but their compositions are challenging to determine, even with JWST. Here, we present the first JWST spectroscopic study of the warm sub-Neptune GJ 3090 b (2.13 R⊕, Teq,A = 0.3 ∼ 700 K), which orbits an M2V star, making it a favorable target for atmosphere characterization. We observed four transits of GJ 3090 b: two each using JWST NIRISS/SOSS and NIRSpec/G395H, yielding wavelength coverage from 0.6 to 5.2 μm. We detect the signature of the 10833 Å metastable helium triplet at a statistical significance of 5.5σ with an amplitude of 434 ± 79 ppm, marking the first such detection in a sub-Neptune with JWST. This amplitude is significantly smaller than predicted by solar-metallicity forward models, suggesting a metal-enriched atmosphere that decreases the mass-loss rate and attenuates the helium feature amplitude. Moreover, we find that stellar contamination, in the form of the transit light source effect, dominates the NIRISS transmission spectra, with unocculted spot and faculae properties varying across the two visits separated in time by approximately 6 months. Free retrieval analyses on the NIRSpec/G395H spectrum find tentative evidence for highly muted features and a lack of CH4. These findings are best explained by a high-metallicity atmosphere (>100× solar at 3σ confidence for clouds at ∼μbar pressures) using chemically consistent retrievals and self-consistent model grids. Further observations of GJ 3090 b are needed for tighter constraints on the atmospheric abundances and to gain a deeper understanding of the processes that led to its potential metal enrichment.