7538 20250204122930.0 CTALK-2025-0066 Hakim, Kaustubh Magma-Atmosphere Coupling of Sub-Neptune Exoplanets 2024 2024-09-12 Atmospheres of hot sub-Neptunes (equilibrium temperatures > 1000 K) are being characterised by the James Webb Space Telescope (JWST). Recent modelling efforts suggest that the magma-atmosphere coupling of hot sub-Neptunes strongly impacts their atmospheric chemistry, enriching the atmosphere in refractory element-bearing gases, e.g., SiO, SiH4. To determine atmospheric chemistry, we implement a new state-of-the-art code, atmodeller, that models an equilibrium chemistry reaction network. Based on the calculations for atmosphere chemistry in the Si-O-H system with mass conservation for H between the atmosphere and the interior, we can classify sub-Neptune populations into steam worlds, hydrogen worlds, and silicon worlds. We quantify the strong impact of including non-ideal gas behaviour and gas solubility in magma on these populations. These populations should exhibit distinct atmospheric signatures that are detectable with JWST transmission and emission spectroscopy. FED-tWIN/ STELLA/ Prf-2021-022 NO Bower, Dan J. Sossi, Paolo Seidler, Fabian Geologica Belgica, Liege, Belgium kaustubh.hakim@ksb-orb.be Contributed CTALKCONT