Structure and dynamics of hot Jupiter atmospheres (Part I)

We study the atmospheric conditions and atmospheric flows of Hot Jupiters, which are – due to their close proximity to the host star – subject to enormous stellar irradiation. Observations suggest that most of the Hot Jupiters feature an anomalously small bulk density (inflated radius) suggesting an impeded thermal evolution and their brightness maximum is displaced eastward from the substellar point pointing towards efficient atmospheric circulation seeking to equilibrate the temperature differences between permanent day and night side. We aim at explaining both observations by modelling the properties of the low-density, yet high-temperature outer atmosphere and the irradiation driven atmospheric flows using 3D MHD approach.
The stellar irradiation induces very high temperatures of up to several thousand Kelvin at the outermost atmospheric layers leading to strong thermal ionisation of alkali metals. We calculate the resulting plasma properties (Rostock group), such as thermal and electrical conductivity, using the relaxation time approximation and coupled non-ideal Saha equations. At the MPS Goettingen the atmospheric circulation driven by the gradients of the irradiation are modelled with and without magnetic effects using fully non-linear numerical MHD models. Combining the electrical conductivity and the vast atmospheric flows shows that Lorentz forces should be taken into account and ohmic dissipation can significantly affect the heat budget.  Further calculating the interior pressure/temperature conditions (Rostock) and extending the atmospheric circulation towards convective regions (MPS Goettingen) helps to refine the results.