Precipitating Condensation Clouds in Substellar Atmospheres

By A. Ackerman, M. Marley. 2001

714 citations recorded by the source corpus.

We present a method to calculate vertical profiles of particle size distributions in condensation clouds of giant planets and brown dwarfs. The method assumes a balance between turbulent diffusion and sedimentation in horizontally uniform cloud decks. Calculations for the Jovian ammonia cloud are compared with results from previous methods. An adjustable parameter describing the efficiency of sedimentation allows the new model to span the range of predictions made by previous models. Calculations for the Jovian ammonia cloud are consistent with observations. Example calculations are provided for water, silicate, and iron clouds on brown dwarfs and on a cool extrasolar giant planet. We find that precipitating cloud decks naturally account for the characteristic trends seen in the spectra of L- and T-type ultracool dwarfs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8bb69eaa48de5ab752dd6e8ecf7942bdf6cf1e8b

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In Astronomy and Astrophysics

Citations in the corpus

Titanium and Vanadium Chemistry in Low-Mass Dwarf Stars (2002, background): “The effective temperatures of M and L dwarfs depend on atmospheric models, for which several different approaches currently exist (see Ackerman & Marley 2001; Allard et al. 2001; Tsuji 2002).”
Spitzer IRAC Photometry of M, L, and T Dwarfs (2006, neutral): “More recently, the models have begun to take into account nonequilibrium chemistry (e.g., Noll et al. 1997; Saumon et al. 2000, 2003, 2006; Burrows et al. 2000; Ackerman & Marley 2001; Allard et al. 2001; Lodders & Fegley 2002; Marley et al. 2002; Tsuji 2002).”
Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, methodology): “As the Ackerman & Marley (2001) model is already implemented in petitRADTRANS, we use its three free parameters to control the mean particle size, cloud mass fraction and particle size distribution independently.”
A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres (2007, methodology): “When including the opacity of clouds, such as Fe-metal and Mg-silicates, we use the cloud model of Ackerman & Marley (2001).”
EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY (2010, methodology): “Clouds are coupled iteratively into the radiative-convective model using the approach of Ackerman & Marley (2001) as described in §1.3.”
Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 (2003, background): “…improving our understanding of cool atmospheres (see Allard et al. 1997 for a review), of the role of dust (Tsuji et al. 1999; Burrows et al. 2000; Ackerman & Marley 2001, Allard et al. 2001; Marley et al. 2002), of irradiation (Saumon et al. 1996; Seager & Sasselov 1998; Sudarsky et al. 2000;…”
Transmission spectral properties of clouds for hot Jupiter exoplanets (2014, background): “Ackerman & Marley (2001) models consider the implications of downward transport of particles by sedimentation, balanced by upward mixing of vapour and condensates, in turn describing a mean global cloud in one-dimension.”
MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY (2010, methodology): “Variations in condensate cloud properties are treated in these models using a sedimentation parameter fsed which is the ratio of the sedimentation velocity to the convective velocity (Ackerman & Marley 2001).”
Dust in brown dwarfs - III. Formation and structure of quasi-static cloud layers (2004, neutral): “This basic scenario has already been proposed by Helling et al. (2001b) and Ackerman & Marley (2001).”
THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, background): “This has been attributed to reduced condensate opacity, as evidenced by strong TiO, Ca I, and Ti I features; and enhanced collision-induced H2 opacity at K-band (e.g. Ackerman & Marley 2001 ;Tsuji et al. 1996; Burgasser et al. 2003a, 2007) .”
LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, methodology): “Various ideas have been put forward to explain the L/T transition including a sudden rain-out of condensates (or equivalently an evolving sedimentation efficiency) (Knapp et al. 2004), or a fragmentation of the cloud layer (Ackerman & Marley 2001; Burgasser et al. 2002).”
MODEL ATMOSPHERES FOR MASSIVE GAS GIANTS WITH THICK CLOUDS: APPLICATION TO THE HR 8799 PLANETS AND PREDICTIONS FOR FUTURE DETECTIONS (2011, background): “…undergoes homogeneous condensation (i.e. vapor and liquid/solid phases composed of the same chemical species), we assume a supersaturation factor of 1% to represent the fraction of iron in the condensed phase (Fegley & Lodders, 1996; Ackerman & Marley 2001; Marley et al. 2002; Burrows et al. 2006).”
Infrared Photometry of Late-M, L, and T Dwarfs (2001, background): “The brightness temperature spectra presented by Ackerman & Marley (2001) show that the near-infrared Ñuxes of L dwarfs may be strongly a†ected by dust cloud behavior.”
L and T Dwarf Models and the L to T Transition (2005, methodology): “For our subsequent model E spectra, we chose s1 = 6 to reflect our prejudice that the refractory clouds made up of large particles settle more compactly than terrestrial water clouds (Ackerman & Marley 2001).”
The effect of condensates on the characterization of transiting planet atmospheres with transmission spectroscopy (2005, methodology): “2, along with the Ackerman & Marley (2001) cloud model with fsed = 2, to compute the normal optical depth of a MgSiO3 cloud with a base at 30 mbar.”
A COMBINED SUBARU/VLT/MMT 1–5 μm STUDY OF PLANETS ORBITING HR 8799: IMPLICATIONS FOR ATMOSPHERIC PROPERTIES, MASSES, AND FORMATION (2011, background): “The two processes may be tied together: Ackerman and Marley (2001) show that clouds may become patchy as they sediment below photospheric pressures.”
Exoplanet Atmospheres: Physical Processes (2010, methodology): “Work on cloud modeling (Ackerman and Marley 2001; Cooper et al. 2003) and atmospheric circulation (Showman & Guillot 2002; Cho et al. 2003) followed soon thereafter.”