{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/irradiation-driven-escape-of-primordial-1","title":"Irradiation-driven escape of primordial planetary atmospheres II. Evaporation efficiency of sub-Neptunes through hot Jupiters","arxiv_id":"2112.00744","date":"2021-12-01","proceeding":null,"authors":["Andrea Caldiroli","Francesco Haardt","Elena Gallo","Riccardo Spinelli","Isaac Malsky","Emily Rauscher"],"abstract":"Making use of the publicly available 1D photoionization hydrodynamics code ATES we set out to investigate the combined effects of planetary gravitational potential energy ($\\phi_p\\equiv GM_p/R_p$) and stellar X-ray and Extreme Ultraviolet (XUV) irradiation ($F_{\\rm XUV}$) on the evaporation efficiency ($\\eta$) of moderately-to-highly irradiated gaseous planets, from sub-Neptunes through hot Jupiters. We show that the (known) existence of a threshold potential above which energy-limited escape (i.e., $\\eta\\simeq 1$) is unattainable can be inferred analytically. For $\\log \\phi_p\\gtrsim \\log \\phi_p^{\\rm thr}\\approx [12.9-13.2]$ (in cgs units), most of the energy absorption occurs where the average kinetic energy acquired by the ions through photo-electron collisions is insufficient for escape. This causes the evaporation efficiency to plummet with increasing $\\phi_p$,. Whether or not planets with $\\phi_p\\lesssim \\phi_p^{\\rm thr}$ exhibit energy-limited outflows is regulated primarily by the stellar irradiation level. Specifically, for low-gravity planets, above $F_{\\rm XUV}\\simeq 10^{4-5}$ erg cm$^{-2}$s$^{-1}$ Ly$\\alpha$ losses overtake adiabatic and advective cooling and the evaporation efficiency of low-gravity planets drops below the energy-limited approximation, albeit remaining largely independent of $\\phi_p$Further, we show that whereas $\\eta$ increases as $F_{\\rm XUV}$ increases for planets above $\\phi^{\\rm thr}_p$, the opposite is true for low-gravity planets. This behavior can be understood by examining the relative fractional contributions of advective and radiative losses as a function of atmospheric temperature. This novel framework enables a reliable, physically motivated prediction of the expected evaporation efficiency for a given planetary system; an analytical approximation of the best-fitting $\\eta$ is given in the appendix.","url_abs":"https://arxiv.org/abs/2112.00744v2","url_pdf":"https://arxiv.org/pdf/2112.00744v2.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"irradiation-driven-escape-of-primordial-1","repo_url":"https://github.com/AndreaCaldiroli/ATES-Code","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}