Exoclimes_Conference_booklet1

ongoing. This will help us understand, for given circumstances, how a planetary magnetic
field could alter the wind structure on hot Jupiters and its effects on day-night temperature
variations and planetary radii.
Extended ionospheres on extrasolar giant planets!
Tommi! Koskinen — University of Arizona
Recent work on close-in extrasolar giant planets (EGPs) raises the possibility that their
atmospheres are significantly affected by ion drag and Joule heating arising from thermal
ionization of their atmospheres (e.g., Cho 2008, Batygin et al. 2010, Perna et al. 2010a,b).
It is unclear, however, if large scale current systems are supported in the relatively weakly
ionized atmospheres of close-in EGPs. We explore thermal ionization and photoionization
of EGP atmospheres, and use the results to constrain the electrodynamic regimes at
pressures ranging from 1 bar to the escaping thermosphere. In line with planetary
atmospheres in the solar system, we find that the coupling of the ions to the neutral
atmosphere is important at all pressure levels. Assuming a magnetic field similar to that of
Jupiter, we find that both the electrons and ions are collisionally coupled to the neutrals
below the 0.1-1 mbar level, but significant ion drag and Joule heating are possible at
pressures lower than this. The conductivities that we calculate, however, imply that the
upper atmospheres of close-in EGPs occupy a regime closer to the solar chromosphere
than planetary ionospheres in the solar system — even at relatively high pressures in the
stratosphere. Nevertheless, the generalized Ohm’s law for partly ionized media is still
valid and we explore the resulting current systems based on this assumption.
3-D modeling of atmospheric escape from Hot Jupiters !
Alain Lecavelier — Institut d'Astrophysique de Paris!
Transit observations in the Lyman-alpha line of the hot Jupiters HD209458b and
HD189733b revealed strong signatures of neutral hydrogen escaping the planet's
atmospheres. We will present our 3D particle model of the dynamics of the escaping
atoms, which is used to calculate theoretical absorption profiles, and can be directly
compared to the observations to constrain the physical conditions at high altitudes in the
exosphere (such as the escape rate and the stellar ionizing flux). Recently, this model has
also been used to interpret the observation of neutral magnesium probing the
thermosphere-exosphere transition region. Simulations show the major influence of the
stellar radiation pressure on the structure of the escaping gas cloud, which can also be
shaped by stellar wind interactions, planetary gravity and self-shielding effects. This results
in spectro-temporal variations of the absorption profile that could be used to further
characterize the atmospheric escape. On a wider scale, our model can be used as a
predictive tool to identify evaporating exoplanets with high-significance absorption
features.
Non-hydrostatic, deep-atmosphere hot Jupiter climate models
Nathan Mayne — University of Exeter!
We present results for the climate of hot Jupiter HD209458b derived using a global
circulation model (GCM) which, using the same numerical scheme, can solve both the full
unsimplified dynamical equations for a rotating atmosphere, as well as including increasing
simplification to these equations. Our results show that the bulk atmospheric flow is largely
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