Since the discovery in 1995 of the first exoplanet orbiting a solar-type star, more than 5,500 exoplanets have been identified, revealing a remarkable diversity of exoplanetary systems. While many of their physical parameters are now well understood, the characterisation of exoplanetary magnetic fields remains largely unexplored, despite its critical role in atmospheric retention. To better understand exoplanetary magnetic fields, star-planet magnetic interactions present a promising avenue of investigation. Such interactions have been observed in HD 189733 which features a hot Jupiter discovered in 2005 with an atmosphere composed of H2O, CO, CH4, CO2, and Na. This system is therefore ideal for studying magnetic coupling in exoplanetary atmospheres, by better understanding star-planet magnetic interactions.

The poster presents a stellar wind model that simulates the theoretical power generated by the magnetic interactions between a star and its planet in the HD 189733 system. Two versions of the model are discussed: a polytropic version, and a more sophisticated version in which the stellar wind is heated and accelerated by Alfvén waves. These same waves can also be excited by the presence of a planet when it is sufficiently close to its star (within the so-called Alfvén surface), propagating towards the star and forming what are known as “Alfvén wings”. Star-planet magnetic interactions can only occur when the planet's orbit falls within the theoretical surface delimited by these wings.

The results of the HD 189733 system models have revealed that the planetary orbit of HD 189733b primarily resides within the Alfvén surface, making this system likely to host star-planet magnetic interactions. This suggests that HD 189733b could host a magnetic field capable of driving these interactions. The two models are driven using a Zeeman Doppler-Imaging magnetic map from 2023 spectro-polarimetric observations, showing that incorporating Alfvén wave heating is crucial for accurately reproducing star-planet magnetic interactions. Modelling such physical processes is thus a promising approach for characterising exoplanetary magnetic fields, and could significantly help us understanding magnetic coupling in exoplanetary atmospheres.

How to cite: Gourvès, C. and Strugarek, A.: The role of magnetic coupling in exoplanet atmospheres: insights from star-planet magnetic interactions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2525, https://doi.org/10.5194/egusphere-egu25-2525, 2025.

Magnetic fields are expected to influence the atmospheric dynamics of hot and ultra-hot Jupiters; however, due to the disparate conditions between the day and night sides, modelling their impact can be difficult.  To make the problem tractable, interactions with the magnetic field are often reduced to the inclusion of a magnetic drag term.  In this talk,  I will demonstrate the impact of vertical and meridional drag from a background dipole magnetic field on the flows in hot Jupiter atmospheres and show that the inclusion of meridional and vertical drag can limit flows over the poles and create a relatively static dayside hot spot around the substellar point, something not seen in models that only consider zonal drag.

How to cite: Christie, D.: Geometric Considerations in Hot Jupiter Magnetic Drag Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20060, https://doi.org/10.5194/egusphere-egu25-20060, 2025.

With the development of ever-improving telescopes capable of observing exoplanet atmospheres, there is a growing demand for enhanced 3D climate models to support and help interpret observational data. However, the computationally intensive and time-consuming nature of General Circulation Models (GCMs) poses significant challenges for simulating a wide range of exoplanetary atmospheres. These challenges are further amplified by the need to rerun every simulation when altering the inner workings of the GCM, such as updating physical assumptions, which makes exploring new physical scenarios difficult.

Grid studies have been employed to explore parameter spaces, but this approach introduces additional complexity with each varying parameter. To address these limitations, a machine learning approach was applied to interpolate a grid of GCM simulations, done with the ExoRad package, representing hot Jupiters orbiting different host stars at varying distances. The performance of our machine learning frameworks in capturing 3D temperature and wind structures to bridge gaps in the model grid will be discussed. Furthermore, it will be explored how these predictions are reflected in simulated transmission spectra that compare to observational properties of space missions like CHEOPS, JWST and PLATO. This work is part of our science support efforts within the PLATO WPs 116700 and 116800.

How to cite: Plaschzug, A., Reza, A., Carone, L., and Helling, C.: Interpolating a Grid of GCM-Simulated Tidally Locked Gaseous Exoplanets Using Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4212, https://doi.org/10.5194/egusphere-egu25-4212, 2025.

With the new generation of space missions like JWST, CHEOPS and PLATO, the characterisation of gas giant planets like WASP-17 b, WASP-107 b, WASP-39 b, HD189733 b and WASP-43 b has become possible. The 3D General Circulation Model ExoRad is used to simulate 3D atmosphere structures for exoplanets orbiting M-, K-, G-, F- and A-type stars.  1D profiles are extracted across different locations as input for our kinetic, non-equilibrium cloud model to gain insight on the chemistry and dynamic behaviour of their atmospheres. The Jupiter-sized planets are tidally locked and a wide range of global temperatures (TGlobal = 400K-2600K), resulting in a grid of a total of 60 different simulated planets. This grid serves as input interpretation for JWST, CHEOPS and PLATO data.

Through this hierarchical modelling approach, a deeper understanding of the host star’s influence on the thermodynamic structure of these planets and its effect on the clouds is obtained. Models of formation through nucleation, surface growth, evaporation, and gravitational settling, consistent with element conservation, are used to calculate the nucleation rate, the local average particle size and the cloud particle composition.

A systematic comparison of atmosphere and cloud structures is possible based on our exoplanet model grid. Here, an in-depth examination of the iron composition of the cloud particle was conducted, focusing on where it is found in the atmosphere across different pressure regimes. This work is part of our science support efforts within the PLATO WPs 116700 and 116800.

How to cite: Gernjak, S., Carone, L., and Helling, C.: Where is the iron in cloudy atmospheres of Jupiter-sized exoplanets?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4342, https://doi.org/10.5194/egusphere-egu25-4342, 2025.

Clouds on exoplanets are hypothesized to explain the absence of expected molecular or atomic absorption features in optical and near-infrared spectra. These observations are obtained using space-based telescopes such as CHEOPS, JWST, and the future PLATO mission, as well as ground-based telescopes like the VLT. These clouds form through the condensation of thermally stable materials onto cloud condensation nuclei (CCN) via gas-surface reactions, playing a crucial role in shaping the observed atmospheric properties. In rocky exoplanets, CCN are supplied by processes such as sandstorms, combustion, and volcanic eruptions. However, gaseous exoplanets lack direct sources of CCN. Instead, CCN form through a bottom-up nucleation process, where small molecules like TiO₂ undergo a series of chemical reactions to form larger molecular clusters [(TiO₂)_N], which grow until they reach a size sufficient to undergo a phase transition from gas to solid, ultimately forming CCN. Previous studies have explored nucleation using various theories, including Classical Nucleation Theory, Modified Classical Nucleation Theory, Non-Classical Nucleation theory, and Kinetic Nucleation Networks. All these approaches require thermochemical data for the nucleating species. While experimental studies have provided insights, limitations in replicating substellar atmospheric conditions, such as extreme temperatures and pressures, hinder their applicability. Quantum mechanical methods have been employed to address these challenges by optimizing cluster geometries and calculating thermochemical properties. However, these computationally expensive methods can take weeks to months for big clusters.

This project utilizes machine learning (ML) models to predict the geometric and thermochemical properties of large molecular clusters. The initial objective involves developing a comprehensive data catalog by integrating in-house molecular data with information from the literature. The dataset is utilized to train the ML models, which are then employed to predict the structural and thermochemical properties of larger molecular clusters. The ultimate goal is to identify clusters capable of undergoing phase transitions from the gas phase to the solid phase, serving as cloud condensation nuclei (CCN) essential for cloud formation in gaseous exoplanets. This work aligns with the scientific objectives of PLATO Work Packages 116700 and 116800. Additionally, it complements the goals of JWST Proposal 6045 (Cycle 3), titled “Detecting Ongoing Gas-to-Solid Nucleation on the Ultra-Hot Planet WASP-76 b”, which aims to observe a single transit of WASP-76 b using MIRI/LRS.

How to cite: Bisht, D., Helling, C., Reza, A., Molinos, H. L., and Aichhorn, M.: Machine Learning-Driven Insights into Cloud CondensationNuclei Formation in Gaseous Exoplanet Atmospheres, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7002, https://doi.org/10.5194/egusphere-egu25-7002, 2025.

A major challenge for exoplanet science is to understand the connection between the atmosphere and the interior of exoplanets in order to understand their origins, structure and evolution [Fortney et al. ]. The observed chemical composition can be affected by the conditions in the deep atmosphere (intrinsic temperature, vertical mixing, interaction with a magma ocean,…), while measuring the atmospheric composition can help to break some degeneracies in the interior of exoplanets. Atmosphere-interior retrievals combining spectroscopic data with mass and radius measurements have been successfully applied to JWST observations of the warm Neptune WASP-107 b [Sing et al. 2024, Welbanks et al. 2024]. They revealed a high internal heat flux and large core, with some differences between the two studies (M_core=11.5+/-3 M_Earth for Sing et al. 2024 and M_core >22 M_Earth for Welbanks et al. 2024).

Here we use the coupled atmosphere-interior model called HADES [Wilkinson et al. 2024] to derive planetary properties (core mass, metallicity and intrinsic temperature) of giant exoplanets. First, we compare our results for WASP-107 b with previous measurements. Then we apply our model to a sample of giant exoplanets to derive trends with planetary mass and irradiation.

References

Fortney et al., JGR Planets, 2021

Sing et al., Nature, 2024

Welbanks et al., Nature, 2024

Wilkinson et al., A&A, 2024

How to cite: Perrier, B., Charnay, B., and Wilkinson, C.: Characterization of the interior of giant exoplanets with JWST transit observations and a coupled atmosphere-interior model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13126, https://doi.org/10.5194/egusphere-egu25-13126, 2025.

Hycean planets are exoplanets characterized by water oceans and hydrogen-rich atmospheres. These planets are high-priority targets for biosignature searches, thanks to their abundant surface liquid water combined with having easy-to-characterize hydrogen-rich atmospheres. The climates and potential habitability of hycean planets are still poorly understood, however. One of their most unusual climate features is moist convection inhibition. In a hydrogen-rich atmosphere the presence of H2O can suppress moist convection and dramatically alter a planet’s temperature structure, an effect which so far has largely been studied for gas giants in the Solar System. This work develops pen-and-paper theory to analyze the effects of moist convective inhibition on hycean planets. The theory is tested and verified against a one-dimensional radiative-convective model. We show that hycean planets with moderately thick atmospheres can exhibit climate bistability. The bistability arises because when the inhibition occurs, the cooling in the upper atmosphere can offset the radiative effect of surface warming, which is most effective when the total optical thickness is slightly greater than unity. In addition, our results show that climates of hycean planets are highly sensitive to small-scale vertical diffusion in the inhibition layer. This diffusion is determined by a wide range of processes which are difficult to resolve in 1D models, such as convective overshoot and large-scale horizontal shear. Our results suggest that hycean planets have unexpectedly rich climate dynamics, and highlight the importance of sophisticated 3D modeling for understanding the potential habitability of hycean worlds

How to cite: Gao, Y., Koll, D., and Ding, F.: Possible climate bistability on hycean planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4899, https://doi.org/10.5194/egusphere-egu25-4899, 2025.

The Large Interferometer For Exoplanets (LIFE) is a proposed space mission that enables the spectral characterization of the thermal emission of exoplanets in the solar neighborhood. The mission is designed to search for global atmospheric biosignatures on dozens of temperate terrestrial exoplanets and it will investigate the diversity of other worlds, following in the footsteps of the current and next-generation exoplanet space missions, JWST, TESS, CHEOPS, Ariel, and PLATO. Here, we will present an update on the latest concept and science case developments of the LIFE collaboration, focusing on the recent publications Alei et al. (2024) and Cesario et al. (2024). Combined observations in the UV/VIS/NIR+MIR observations with HWO +  LIFE would provide synergistic constraints on temperate terrestrial exoplanets, including the atmospheric thermal profile to ~10 K uncertainty, and decisively constrain atmospheric abundances of CO₂, H₂O, O₂, and O_3, and weakly constrain CO and CH₄ (Alei et al. 2024). Exploration of young planetary systems in nearby young stellar associations with the LIFE mission will enable the rapid (~min to hr) detection of terrestrial protoplanets in their magma ocean phase, both for M and G dwarfs, which would enable constraints on the transition from primary to secondary atmospheres (Cesario et al. 2024). Characterization of the atmospheres of terrestrial exoplanets in time enables constraints on prebiotic chemical environments and the near-surface habitability of young and mature terrestrial exoplanets.

References:

Alei, E. et al.  (2024). Large Interferometer For Exoplanets (LIFE): XIII. The Value of Combining Thermal Emission and Reflected Light for the Characterization of Earth Twins. Astronomy & Astrophysics 689, A245.

Cesario, L. et al.  (2024) Large Interferometer For Exoplanets (LIFE)-XIV. Finding terrestrial protoplanets in the galactic neighborhood. Astronomy & Astrophysics 692, A172.

How to cite: Lichtenberg, T., Alei, E., Cesario, L., Quanz, S., Glauser, A., Angerhausen, D., Rugheimer, S., Kammerer, J., Fortier, A., Ireland, M., Defrere, D., Linz, H., Noack, L., Braam, M., and Collaboration, L.: The Large Interferometer For Exoplanets (LIFE): synergy with HWO & protoplanet detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4223, https://doi.org/10.5194/egusphere-egu25-4223, 2025.