Toward 3D photochemical modeling of exoplanet atmospheres

Thursday 5 July, 17:30

The study of exoplanets has evolved from detection to characterization. Determining and interpreting the chemical composition is one of the key questions in atmospheric characterization. 1D photochemical models track the kinetics of the gas-phase species and are useful to determine the steady-state abundances. However, when applying the model to the diversity of exoplanets, they suffer from neglecting the 3D atmospheric dynamics. Motivated by the work of Cooper & Showman, we revisit the chemical relaxation method, which seeks to enhance the computational efficiency of chemical-kinetics calculations by replacing the chemical network with a handful of independent source/sink terms. We generalize the treatment by developing a pathway analysis tool that allows us to identify the rate-limiting reaction to estimate the timescale as a function of temperature and pressure. We validate the chemical relaxation method against full chemical kinetics calculations for WASP-18b-, HD 189733b- and GJ 1214-b-like atmospheres. Finally, we apply the chemical relaxation method to WASP-43b using a 3D Global Circulation Model to show the disequilibrium effects of CO, CO2, H2O, and CH4.

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