7539 20250204123050.0 CTALK-2025-0067 Hakim, Kaustubh Magma-Atmosphere Coupling of Hot Sub-Neptunes 2024 2024-10-29 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. We model an equilibrium chemistry reaction network to simulate magma-atmosphere reactions. 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 now and with ARIEL in the future. These modelling results can help ARIEL to prioritise the target list. FED-tWIN/ STELLA/ Prf-2021-022 NO ARIEL Consortium Meeting, Lisbon, Portugal kaustubh.hakim@ksb-orb.be Contributed CTALKCONT