Dust Opacities

Min, M.

doi:10.1051/epjconf/201510200005

Cited by 9 publications

(10 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A distribution of these particles with different fractions of volume being the vacuum core are then averaged over. This represents well the distributions of irregularly shaped particles for protoplanetary disks, both in the Rayleigh regime and for larger particles (Min et al 2003(Min et al , 2008Min 2015), and has now also been implemented in atmospheric models ATRES (Stolker et al 2017), PetitCODE (Mollière et al 2015(Mollière et al , 2017, ARCiS (Ormel & Min 2019;Chubb et al 2020) and also in retrievals PetitRADTRANS (Mollière et al 2019).…”

Section: Observational Implicationsmentioning

confidence: 86%

Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)

Helling

Lewis

Samra

et al. 2021

A&A

View full text Add to dashboard Cite

Context. Ultra-hot Jupiters are the hottest exoplanets that have been discovered so far. Observations begin to provide insight into the composition of their extended atmospheres and their chemical day/night asymmetries. Both are strongly affected by cloud formation. Aims. We explore trends in cloud properties for a sample of five giant gas planets: the hot gas giant WASP-43b and the four ultra-hot Jupiters (UHJs) WASP-18b, HAT-P-7b, WASP-103b, and WASP-121b. This provides a reference frame for cloud properties for the JWST targets WASP-43b and WASP-121b. We further explore chemically inert tracers to observe geometrical asymmetries of UHJs and if the location of the inner boundary of a 3D global circulation model (3D GCM) matters for the clouds that form. Methods. A homogeneous set of 3D GCM results was used as input for a kinetic cloud formation code to evaluate the cloud opacity and gas parameters such as C/O, mean molecular weight, and degree of ionisation. We cast our results in terms of integrated quantities to enable a global comparison between the sample planets. Results. The large day/night temperature differences of UHJs cause the following chemical asymmetries: cloud-free days but cloudy nights, atomic versus molecular gases and their different mean molecular weights, deep thermal ionospheres versus low-ionised atmospheres, and undepleted versus enhanced C/O. WASP-18b, as the heaviest planet in the sample, has the lowest global C/O. Conclusions. The global climate may be considered as similar amongst UHJs, but different to that of hot gas giants. The local weather, however, is individual for each planet since the local thermodynamic conditions, and hence the local cloud and gas properties, differ. The morning and the evening terminator of UHJs will carry signatures of their strong chemical asymmetry such that ingress and egress asymmetries can be expected. An increased C/O ratio is a clear sign of cloud formation, making cloud modelling a necessity when utilising C/O (or other mineral ratios) as a tracer for planet formation. The changing geometrical extension of the atmosphere from the day to the nightside may be probed through chemically inert species such as helium. Ultra-hot Jupiters are likely to develop deep atmospheric ionospheres which may impact the atmosphere dynamics through magneto-hydrodynamic processes.

show abstract

Section: Observational Implicationsmentioning

confidence: 86%

Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)

Helling

Lewis

Samra

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…For the same parameters (c i = c j ), the matrix (m) i j coincides with the identity matrix. Equations (17) imply that z sca = −A 11 A −1 31 z in , and as a result we obtain the so-called " spheroidal" (since expansions in spheroidal functions are used) T -matrix for the potential p:…”

Section: Solution Of the Axisymmetric Problemmentioning

confidence: 99%

“…The disadvantage of the approach is that the computational problems for spheroids increase rapidly with increasing diffraction parameter, ratio of semiaxes, or refractive index. In particular, in astrophysical applications the first one and sometimes the second one [16,17] are critical, while in microwave experimentsthe third one [18]. In addition to those listed above, to calculate the optical properties of spheroids one can apply universal methods developed for particles of arbitrary shape and structure (see, for example, the review in [19]).…”

Section: Introductionmentioning

confidence: 99%

On relations of the T-matrices arising in the axisymmetric problem of light scattering by a spheroid

Фарафонов

Ильин

D.G.

2022

Optics and Spectroscopy

View full text Add to dashboard Cite

The relations between the T-matrices emerging when solving the problem of light scattering by a spheroid by applying the expansions of the electro-magnetic fields in the employing spheroidal and spherical bases are found. The behavior of the obtained relations is numerically studied, and it is noted that in a wide range of the task parameter values the calculation of the spheroidal T-matrix and its corresponding transformation is the only practical way to derive the spherical T-matrix often used in applications. Keywords: light scattering, T-matrix.

show abstract

“…The authors found good agreement between the three distributions considered for the Rayleigh regime (Min et al 2003), and they further found that hollow spheres replicate laboratory experiments of irregularly shaped quartz particles well (Min et al 2005) for larger particles. We used the distribution of hollow spheres because it can be calculated using an extension of the Mie theory and thus yields very fast results (Min 2015).…”

Section: Particle Shapementioning

confidence: 99%

Mineral snowflakes on exoplanets and brown dwarfs

Samra

Helling

Min

2020

A&A

View full text Add to dashboard Cite

Context. Exoplanet atmosphere characterisation has become an important tool in understanding exoplanet formation, evolution, and it also is a window into potential habitability. However, clouds remain a key challenge for characterisation: upcoming space telescopes (e.g. the James Webb Space Telescope, JWST, and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey) and ground-based high-resolution spectrographs (e.g. the next-generation CRyogenic high-resolution InfraRed Echelle Spectrograph) will produce data requiring detailed understanding of cloud formation and cloud effects for a variety of exoplanets and brown dwarfs. Aims. We aim to understand how the micro-porosity of cloud particles affects the cloud structure, particle size, and material composition on exoplanets and brown dwarfs. We further examine the spectroscopic effects of micro-porous particles, the particle size distribution, and non-spherical cloud particles. Methods. We expanded our kinetic non-equilibrium cloud formation model to study the effect of micro-porosity on the cloud structure using prescribed 1D (Tgas–pgas) profiles from the DRIFT-PHOENIX model atmosphere grid. We applied the effective medium theory and the Mie theory to model the spectroscopic properties of cloud particles with micro-porosity and a derived particle size distribution. In addition, we used a statistical distribution of hollow spheres to represent the effects of non-spherical cloud particles. Results. Highly micro-porous cloud particles (90% vacuum) have a larger surface area, enabling efficient bulk growth higher in the atmosphere than for compact particles. Increases in single scattering albedo and cross-sectional area for these mineral snowflakes cause the cloud deck to become optically thin only at a wavelength of ~100 μm instead of at the ~20 μm for compact cloud particles. A significant enhancement in albedo is also seen when cloud particles occur with a locally changing Gaussian size distribution. Non-spherical particles increase the opacity of silicate spectral features, which further increases the wavelength at which the clouds become optically thin. Conclusions. Retrievals of cloud properties, particularly particle size and mass of clouds, are biased by the assumption of compact spherical particles. The JWST mid-infrared instrument will be sensitive to signatures of micro-porous and non-spherical cloud particles based on the wavelength at which clouds are optically thin. Details of spectral features are also dependent on particle shape, and greater care must be taken in modelling clouds as observational data improves.

show abstract

Dust Opacities

Cited by 9 publications

References 22 publications

Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)

Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)

On relations of the T-matrices arising in the axisymmetric problem of light scattering by a spheroid

Mineral snowflakes on exoplanets and brown dwarfs

Contact Info

Product

Resources

About