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Combined atmosphere-magnetosphere modeling of TRAPPIST-1h to discern the atmospheric profile

Presentation #102.246 in the session Poster Session.

Published onJun 20, 2022
Combined atmosphere-magnetosphere modeling of TRAPPIST-1h to discern the atmospheric profile

The modeling of various exoplanet physical domains (e.g. atmosphere and magnetosphere) is usually performed independently for each domain despite their considerable mutual interactions. The upper layer of the atmosphere is photoionized by stellar irradiation which impacts the ionospheric conductivity. The conductivity, in turn, controls the closure of magnetospheric field-aligned (Birkeland) currents in the ionosphere while the interaction between the stellar wind and the planetary magnetosphere influences the rate of atmospheric loss. Additionally, observations of exoplanetary atmospheres alone cannot fully disambiguate fundamental properties such as the surface density, temperature and pressure, and so examining the implications of these atmospheric profiles on coupled systems helps to constrain the viable parameter space and provide a more complete understanding of the system as a whole. In this work, we explore whether TRAPPIST-1h could have a Titan-like atmosphere. We consider a range of atmospheric compositions and surface conditions as inputs to a photochemical model, which is then used to inform the conductivity and exosphere profile used by the GAMERA stellar wind-magnetosphere magnetohydrodynamic (MHD) model. The atmospheric loss rate as a result of charge exchange is calculated, as well as the signature of the resulting energetic neutral atoms on Lyman-alpha absorption as a function of velocity. Should such a signal be detectable, this approach demonstrates a method of leveraging various observations to constrain exoplanet properties across many physical domains.

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