Structure and dynamics of hot Jupiter Atmospheres (Part II)

Exoplanetary research is a fast growing and fascinating field of science. Many surprising discoveries have already fundamentally changed our perception of planetary physics. Hot Jupiters, large gas planets that orbit their parent stars in close proximity, were the first exoplanets to be detected and remain the best characterised. 

Among the striking properties of these extreme planets are extreme surface temperatures of up to 3000 K and often anomalously small densities – they appear inflated. In addition, their brightness pattern deviates from the expected radiation equilibrium. The day-to-night side brightness contrast and the displacement of the hottest spot reveal a diverse impact of the atmospheric dynamic. Inflation can be explained by depositing heat into the deeper interior, either by tidal interaction, vertical advection, viscous dissipation or ohmic dissipation. The latter effect is particularly important when fast atmospheric winds, sizeable electrical conductivities, and a strong interior magnetic field conspire to induce significant electric currents.

Two groups with complementary expertise will continue their collaborative effort to model the atmospheric dynamics of gas planets. The Planetary Dynamics group at the Max Planck Institute for Solar System Research in Göttingen has already characterised the non-magnetic dynamics in the radiative outer zone using the well-established code MagIC. For the second funding period, the Göttingen group proposes to extend the simulations by including magnetic effects and adding a deeper convective (dynamo) region. Implementing the huge lateral variations in the temperature-dependent electrical conductivity will prove particularly interesting, yet numerically challenging. The resulting 3D temperature structure will form the basis for computing synthetic phase curves which can be directly confronted with observations.

The Statistical Physics group at the University of Rostock provides electrical conductivity and other essential properties. So far, the group has calculated the coupled ionisation reactions of hydrogen, helium, and of metals in the highly irradiated part of the atmosphere.  Subsequently the electrical conductivity was computed, using a modified version of the COMPTRA code generalized for multi-component plasmas. For the second funding period, the Rostock group proposes to perform quantum-statistical ab-initio simulations (DFT-MD method), appropriate for the deeper interior, in order to compute transport properties, such as electrical conductivity, along the adiabatic interior of Hot Jupiters.  A combination of both approaches will yield consistent properties for regions modeled by the Göttingen Group.

The ultimate goal is to explain the observed inflation and, based on the dynamically modified temperature distribution, the observed brightness pattern (Spitzer, HST, Kepler, JWST).