Exoclimes_Conference_booklet1

which cloud-induced temporal variability has been observed, but so far the
characterization of these complex & dynamic atmospheres has been limited to lowresolution
spectroscopy and photometry. We will present Doppler Imaging of a brown
dwarf’s surface using high-resolution near-infrared spectroscopy. Future such observations
will track the formation, evolution, and breakup of global weather patterns, and will provide
revolutionary new benchmarks against which to compare global circulation models of
cloudy substellar objects.
Ionisation regimes structuring planetary atmospheres!
Christiane Helling — University of St Andrews!
The steady increase of the sample of extrasolar planets broadens our knowledge and at
the same time, reveals our lack of understanding fundamental processes. For example
does the habitability of a planet depend, amongst other things, on how much and which
radiation reached the ground, how clouds form and which effect clouds have on the
composition and on the electric state of the ambient gas from which they form.
We have studied the formation of mineral clouds on planetary atmospheres by a kinetic
approach which allows us to predict the size distribution and material composition of the
cloud particles. These results have been used to study if such clouds can be charged and
under which conditions an electric field breakdown, such as lightning or other transient
luminous events, may occur. Our results suggest that different intra-cloud discharge
processes dominate at different heights inside a cloud, and that the atmospheric volume
affected by large-scale lightening discharges is larger in Brown Dwarfs than in planetary
atmospheres. We demonstrate how different ionisation processes suggest that planets and
brown dwarfs have stratified ionised atmospheres.
Atmospheric cloud models from brown dwarfs to exoplanets
Derek Homeier -- Centre de Recherche Astrophysique de Lyon/ENS-Lyon!
State-of-the-art theoretical models of low-mass stars and brown dwarf atmospheres aim at
a physically and chemically consistent simulation, generally evolving from the assumptions
of hydrostatic and radiative equilibrium as well as a chemical equilibrium composition
based on given input abundances. In further refinement more complex phenomena such
as atmospheric dynamics and departures from chemical equilibrium by advection,
photochemistry or condensate formation can be considered. This approach has allowed
model grids based on a minimal set of parameters to reproduce observed properties of
substellar objects with considerable success. Most important among these is without doubt
the role of cloud opacity throughout the sequence from late-type stars to the coolest brown
dwarfs known to date. I will present the results of the PHOENIX Settling models, which
successfully describe the formation of different cloud types, from iron and silicate dust
dominating in L dwarfs over sulphides and halides that become relevant in cooler T dwarfs,
to the appearance of water ice and colder condensates in the latest Y dwarfs. These
models can often be applied with little modification to lower mass objects such as directly
imaged gas giants, highlighting the effects of lower gravity on atmospheric chemistry and
cloud formation. However, as one explores more fully the domain of exoplanet
atmospheres, increased complexity like global transport triggered by irradition, and
atmospheric chemistry no longer based on scaled-solar compositions come into play.
Consequently the direct retrieval of atmospheric properties from observed data, is often
preferred in these cases, but with only few data points to constrain the models, may
struggle to produce a unique and physically realistic solution. I shall show here how our
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