3D mixing in hot Jupiters atmospheres. I. Application to the day/night cold trap in HD 209458b

By V. Parmentier, A. Showman, Y. Lian. 2013

280 citations recorded by the source corpus.

Context. Hot Jupiters exhibit atmospheric temperatures ranging from hundreds to thousands of Kelvin. Because of their large daynight temperature differences, condensable species that are stable in the gas phase on the dayside—such as TiO and silicates—may condense and gravitationally settle on the nightside. Atmospheric circulation may counterbalance this tendency to gravitationally settle. This three-dimensional (3D) mixing of condensable species has not previously been studied for hot Jupiters, ye t it is crucial to assess the existence and distribution of TiO and silicates i n the atmospheres of these planets. Aims. We investigate the strength of the nightside cold trap in hot Jupiters atmospheres by investigating the mechanisms and strength of the vertical mixing in these stably stratified atmosphere s. We apply our model to the particular case of TiO to address the question of whether TiO can exist at low pressure in suffi cient abundances to produce stratospheric thermal inversions despite the nightside cold trap. Methods. We modeled the 3D circulation of HD 209458b including passive (i.e.radiatively inactive) tracers that advect with the 3D flow, with a source and sink term on the nightside to represent their condensation into haze particles and their gravitati onal settling. Results. We show that global advection patterns produce strong vertical mixing that can keep condensable species aloft as long as they are trapped in particles of sizes of a few microns or less on the night side. We show that vertical mixing results not from small-scale convection but from the large-scale circulation driven by t he day-night heating contrast. Although this vertical mixi ng is not diffusive in any rigorous sense, a comparison of our results with idealized diffusion models allows a rough estimate of the effective vertical eddy diffusivities in these atmospheres. The parametrization Kzz = 5×10 4 √ Pbar m 2 s −1 , valid from∼1 bar to a fewµbar, can be used in 1D models of HD 209458b. Moreover, our models exhibit strong spatial and temporal variability in the tracer concentration that could result in observable variations during either transit or se condary eclipse measurements. Finally, we apply our model to the case of TiO in HD 209458b and show that the day-night cold trap would deplete TiO if it condenses into particles bigger than a few microns on the planet’s nightside, keeping it from creating the observ ed stratosphere of the planet.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/338b0204c88963964190738606e07771ebb6c3a7

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. Sing
6. V. Parmentier
7. D. Deming
8. M. Line

Citations in the corpus

• A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets (2020, methodology): “The value of Kzz in brown dwarf and exoplanet atmospheres is a long-standing theoretical problem, and several attempts have been made to estimate it from numerical models (e.g. Moses et al. 2011; Parmentier et al. 2013; Zhang & Showman 2018a,b).”
• ExoMol line lists – XVIII. The high-temperature spectrum of VO (2016, background): “…et al. 2009; Fortney et al. 2010; Bowler et al. 2010; Madhusudhan & Seager 2010; Huitson et al. 2012; Spiegel & Burrows 2013; Gibson et al. 2013; Parmentier et al. 2013; Agúndez et al. 2014; Hoeijmakers et al. 2015; Schwarz et al. 2015; Haynes et al. 2015; Wakeford & Sing 2015) about a…”
• THE IMPRINT OF EXOPLANET FORMATION HISTORY ON OBSERVABLE PRESENT-DAY SPECTRA OF HOT JUPITERS (2016, background): “One can then compare typical settling velocities (see Parmentier et al. 2013, their Fig.”
• PLANETARY POPULATION SYNTHESIS COUPLED WITH ATMOSPHERIC ESCAPE: A STATISTICAL VIEW OF EVAPORATION (2014, methodology): “The γ values used in our simulation are shown in Table 2 and are determined by comparing the temperature in the deep isothermal zone of the analytical model (Equation 6) with the results from the line-by-line radiative transfer models (Fortney et al. 2005, 2008; Parmentier et al. 2013b).”
• VULCAN: An Open-source, Validated Chemical Kinetics Python Code for Exoplanetary Atmospheres (2016, background): “…that it takes the form of equator-to-pole circulation cells that extend over several orders of magnitude in vertical/radial pressure (Heng, Frierson & Phillipps 2011; Perna, Heng & Pont 2012; Parmentier et al. 2013; Mendonça et al. 2016), which renders the eddy-diffusion approximation suspect2.”
• Transmission spectral properties of clouds for hot Jupiter exoplanets (2014, methodology): “Models from Parmentier et al. (2013) and Heng & Demory (2013) show that strong vertical mixing can keep micron or sub-micron sized particles aloft in the atmosphere where grain sizes between 0.001 and 100 µm were considered.”
• THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA (2015, background): “First, the meridional circulation can transport condensate material from the equatorial regions to the polar regions, a phenomenon suggested to be common in hot Jupiter and sub-Neptune planets (Parmentier et al. 2013, Charnay et al. 2015a).”
• From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context (2018, methodology): “Whereas this is in line with the expected role played by gravity in the cold trapping of TiO and VO (Parmentier et al. 2013), the lack of spectral features in the even higher gravity WASP-18b (Arcangeli et al. 2018), where the day/night cold trap should play a larger role, makes the presence of an…”
• SPECTROSCOPIC EVIDENCE FOR A TEMPERATURE INVERSION IN THE DAYSIDE ATMOSPHERE OF HOT JUPITER WASP-33b (2015, methodology): “Our inference of TiO supports previous theoretical predictions that TiO should be abundant in the hottest of oxygen-rich hot Jupiters, due to the lack of an effective vertical or day-night cold trap (Perez-Becker & Showman 2013; Parmentier et al. 2013).”
• Extremely Irradiated Hot Jupiters: Non-oxide Inversions, H− Opacity, and Thermal Dissociation of Molecules (2018, background): “In addition to these vertical cold traps, Parmentier et al. (2013) showed that the nightside of an exoplanet like HD 209458b can act as an effective horizontal cold trap.”
• Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects (2019, methodology): “, 172, 182, 68) to three dimensional cloud models (202, 67), as well as detailed studies of clouds microphysics (103).”
• Observing transiting planets with JWST. Prime targets and their synthetic spectral observations (2016, background): “Parmentier et al. (2013b) found in GCM models that the corresponding eddy diffusion coefficient behaves roughly as Kirrad ∝ P−1/2 and two GCMs modeling HD 189733b and HD 209458b have found K209458b = 5 × 108 · ( P 1 bar )−0.5 cm2 s −1 , (A.8) K189733b = 107 · ( P 1 bar )−0.65 cm2 s −1 , (A.9) see…”
• HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013, background): “Parmentier et al. (2013) has explored how a strong day/night temperature contrast can lead to depletion of TiO through the use of 3D modelling.”
• HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering (2014, background): “These estimates are consistent with the more detailed analysis presented in Parmentier et al. (2013).”
• TRANSITIONS IN THE CLOUD COMPOSITION OF HOT JUPITERS (2016, methodology): “However, the small particles and vertically homogeneous cloud we assume, corresponding to a large vertical mixing coefficient, are more in agreement with transmission spectrum observations and theoretical work on vertical mixing Parmentier et al. (2013).”