Dynamics and Disequilibrium Carbon Chemistry in Hot Jupiter Atmospheres, with Application to HD 209458b

By Curtis S. Cooper, A. Showman. 2006

203 citations recorded by the source corpus.

Chemical equilibrium considerations suggest that, assuming solar elemental abundances, carbon on HD 209458b is sequestered primarily as carbon monoxide (CO) and methane (CH4). The relative mole fractions of CO(g) and CH4(g) in chemical equilibrium are expected to vary greatly according to variations in local temperature and pressure. We show, however, that in the p = 1-1000 mbar range, chemical equilibrium does not hold. To explore disequilibrium effects, we couple the chemical kinetics of CO and CH4 to a three-dimensional numerical model of HD 209458b's atmospheric circulation. These simulations show that vigorous dynamics caused by uneven heating of this tidally locked planet homogenize the CO and CH4 concentrations at p < 1 bar, even in the presence of lateral temperature variations of ~500-1000 K. In the 1-1000 mbar pressure range we find that over 98% of the carbon is in CO. This is true even in cool regions where CH4 is much more stable thermodynamically. Our work shows, furthermore, that planets 300-500 K cooler than HD 209458b can also have abundant CO in their upper layers due to disequilibrium effects. We demonstrate several interesting observational consequences of these results.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/4a3dcaf3111488e845b21feecd3b553d2df22d9c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Marley
5. D. Deming
6. D. Sing
7. H. Knutson
8. V. Parmentier

In Statistical and Nonlinear Physics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. Sara Seager
5. H. Knutson
6. V. Parmentier
7. M. Marley
8. M. Line

Citations in the corpus

• Equilibrium chemistry down to 100 K (2017, background): “Griffith & Yelle (1999) and Cooper & Showman (2006) argue for strong chemical dis-equilibrium effects and higher CO abundances in BD and exoplanet atmospheres.”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “The single largest outstanding question centers on the issue of whether or not the chemistry is in equilibrium (e.g., Moses et al. 2011; Visscher & Moses 2011); it is likely that the atmospheric circulation plays an important role in shaping this chemistry (e.g., Cooper & Showman 2006).”
• SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, background): “Due to horizontal quenching (Cooper & Showman 2006; Agúndez et al. 2014), we expect constant dayside abundances at all orbital phases.”
• TRANSMISSION SPECTRA OF THREE-DIMENSIONAL HOT JUPITER MODEL ATMOSPHERES (2009, methodology): “In order to simulate how a fixed CO/CH4 ratio, independent of height and location, would effect these spectra, we have calculated transmission spectra with mixing ratios given by the “cold model” of Cooper & Showman (2006), which is a good approximation for the temperatures of HD 189733b.”
• A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres (2007, unknown): “The planet will appear more homogenized (Seager et al. 2005), as was shown explicitly by Fortney et al. (2006a) for light curves for the Cooper & Showman (2006) 3D dynamical model.”
• Hot nights on extrasolar planets: mid‐infrared phase variations of hot Jupiters (2007, background): “Cooper & Showman (2005, 2006) determine energy recirculation and predict global temperature contrasts of ∼500 K at the photosphere.”
• DISEQUILIBRIUM CARBON, OXYGEN, AND NITROGEN CHEMISTRY IN THE ATMOSPHERES OF HD 189733b AND HD 209458b (2011, methodology): “…on HD 209458b but not HD 189733b, and the identification of longitudinal temperature variations and phase lags (e.g., Knutson et al. 2007, 2009; Cooper & Showman 2006; Fortney et al. 2006a, 2008a, 2010; Richardson et al. 2007; Burrows et al. 2007, 2008; Cowan et al. 2007; Showman et al.…”
• A chemical model for the atmosphere of hot Jupiters (2012, background): “…thermodynamic equilibrium have been discussed with timescale arguments (e.g. Lodders & Fegley 2002; Fortney et al. 2006, 2008b; Visscher et al. 2006, 2010; Madhusudhan & Seager 2010) or modeled with a few reactions describing the CO-CH4 conversion coupled with the dynamics (Cooper & Showman 2006).”
• Atmospheric circulation of tidally locked exoplanets: a suite of benchmark tests for dynamical solvers (2010, methodology): “Rauscher & Menou (2010) interpret this difference as being due to the deeper reservoir of inert (τ rad = ∞) atmospheric layers in the models of Cooper & Showman (2006), which counterbalances the angular momentum of the super-rotating wind higher up in the atmosphere.”
• Atmospheric Circulation of Hot Jupiters: Three-dimensional Circulation Models of HD 209458b and HD 189733b with Simplified Forcing (2008, unknown): “Consistent with the results of Cooper & Showman (2005, 2006), the imposed day-night heating contrasts lead to rapid development of large day-night temperature differences and winds reaching several kmsec - 1 .”
• The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint (2017, background): “It is therefore not likely that the CH4 abundance is enhanced relative to equilibrium abundances due to horizontal or vertical quenching, as has been postulated for many hot Jupiter atmospheres (e.g. Cooper & Showman 2006; Agúndez et al. 2014).”
• The Influence of Atmospheric Dynamics on the Infrared Spectra and Light Curves of Hot Jupiters (2006, methodology): “Here we generate infrared spectraand light curves as a function of orbital phase for the Cooper & Showman (2006) (hereafter: CS06) dynamical simulation.”
• MULTIWAVELENGTH CONSTRAINTS ON THE DAY–NIGHT CIRCULATION PATTERNS OF HD 189733b (2008, methodology): “For the planet’s day side, we show a model that utilizes equilibrium chemical abundances (black), and in red a model that uses a non-equilibrium CH4/CO ratio of 0.014 (CH4 mixing ratio of 7 × 10 −6) as taken directly from Cooper & Showman (2006) and Fortney et al. (2006b).”