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As Above, So Below: Connecting the upper and lower atmospheres of exoplanets via disequilibrium chemistry

Presentation #102.129 in the session Poster Session.

Published onJun 20, 2022
As Above, So Below: Connecting the upper and lower atmospheres of exoplanets via disequilibrium chemistry

An interplay of physical and chemical processes governs the composition of gaseous exoplanet atmospheres. In particular, modelling efforts have demonstrated that photochemical dissociation, vertical mixing, and day-night circulation are strong sources of disequilibrium chemistry, which potentially alter the molecular abundances measured. Transmission spectroscopy can only probe a relatively small region of the planetary atmosphere — roughly between 10 and 100 mbar — but advective processes connect this pressure region with the atmospheric layers above and below. Given the imminent commissioning of the James Webb Space Telescope, understanding the physico-chemical connections in exoplanet atmospheres becomes crucial and timely.

In this presentation, we will discuss two important mechanisms by which disequilibrium chemistry is connecting the upper and lower atmospheres of irradiated exoplanets: vertical mixing from the deeper layers, and photochemical dissociations in the upper layers. For each of these mechanisms we examine their impact in a multi-dimensional model and for a wide range of exoplanets with different effective temperatures and stellar hosts. Finally, we discuss the impact of the deep atmosphere and of photochemistry on transmission spectroscopy, and identify important uncertainties associated with the chemical abundances of irradiated exoplanets.

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