Modeling the Dynamics and Thermochemistry for the Outer Atmospheres of the Ultra-hot Jupiter WASP-121b

[2602.01364] Modeling the Dynamics and Thermochemistry for the Outer Atmospheres of the Ultra-hot Jupiter WASP-121b Skip to main content Search Submit Donate Log in Search arXiv Press Enter to search · Advanced search Astrophysics > Earth and Planetary Astrophysics arXiv:2602.01364 (astro-ph) [Submitted on 1 Feb 2026 ( v1 ), last revised 15 Aug 2026 (this version, v3)] Title: Modeling the Dynamics and Thermochemistry for the Outer Atmospheres of the Ultra-hot Jupiter WASP-121b Authors: Lile Wang , Yiren Lin , Ji Wang , Fei Dai View a PDF of the paper titled Modeling the Dynamics and Thermochemistry for the Outer Atmospheres of the Ultra-hot Jupiter WASP-121b, by Lile Wang and 3 other authors View PDF HTML (experimental) Abstract: We present three-dimensional simulations of the ultra-hot Jupiter (UHJ) WASP-121b from the planetary surface to extended outflows, coupling hydrodynamics with consistent non-equilibrium thermochemistry, ray-tracing radiative transfer, and hydrodynamics using the GPU-accelerated Kratos framework. The fiducial model exhibits several atmospheric layers, including the lower atmospheres controlled by day-night circulation, and transonic photoevaporative outflows at higher altitudes shaped into two spiral arms by the stellar gravity and orbital motion effects. Different species could trace different regions: Fe probes rotation-dominated inner layers, Na maps dense spiral arms where recombination balances photoionization, and H$\alpha$ and He 10830 A features trace progressively more extended, ionized gas. With spiral arm velocities reaching ~ 40 km/s projected along the line of sight, this morphology naturally reproduces the velocity pattern of observed high-velocity Na and H$\alpha$ absorption features without requiring significant super-rotation jet streams, although the absolute absorption amplitudes could carry uncertainties from stellar UV luminosity and trace elemental abundances. Parametric studies reveal complex dependencies on stellar irradiation: enhanced FUV intensifies outflows and extends spiral arms spatially and kinematically, while EUV and X-ray expands spiral structures into attenuated, ionized regions. Stellar wind confinement compresses the dayside outflow and enhances metastable helium absorption. This work demonstrates that current and future transmission spectral observations that probe multiple species can provide important constraints on astrophysical environments of UHJs by comparing state-of-the-art simulations. Comments: 29 pages, 16 figures, accepted for publication in ApJ Subjects: Earth and Planetary Astrophysics (astro-ph.EP) ; Solar and Stellar Astrophysics (astro-ph.SR) Cite as: arXiv:2602.01364 [astro-ph.EP] (or arXiv:2602.01364v3 [astro-ph.EP] for this version) https://doi.org/10.48550/arXiv.2602.01364 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Lile Wang [ view email ] [v1] Sun, 1 Feb 2026 18:03:08 UTC (11,709 KB) [v2] Wed, 22 Jul 2026 07:29:37 UTC (11,198 KB) [v3] Sat, 15 Aug 2026 09:35:58 UTC (11,199 KB) Full-text links: Access Paper: View a PDF of the paper titled Modeling the Dynamics and Thermochemistry for the Outer Atmospheres of the Ultra-hot Jupiter WASP-121b, by Lile Wang and 3 other authors View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.EP < prev | next > new | recent | 2026-02 Change to browse by: astro-ph astro-ph.SR References & Citations NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... 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