Magnetism in Hot Jupiters

Hot Jupiters were the first exoplanets to be observed around main sequence stars and, despite representing only 10% of observed exoplanets, remain some of the best characterised planets outside our solar system, due to their favourable observing conditions.  Although they were discovered nearly 30 years ago, two fundamental physics questions remain: How are they formed and why are they so large? In addition to these two longstanding questions, many new avenues for investigation have arisen due to recent observational advances, including the role of clouds, disequilibrium chemistry and magnetic fields. This proposal will investigate the role of magnetism in hot Jupiters. There are three key reasons for this choice of focus: first, magnetism (via Ohmic dissipation) is one of the leading contenders for explaining the long-standing “radius inflation” problem. Second, magnetism impacts atmospheric dynamics, affecting both the day-night circulation efficiency and the (observable) hot spot displacement.  Finally, the highly inhomogeneous environment plays host to magnetohydrodynamic (MHD) instabilities and dynamics which have received little attention, but may play a role in Hot Jupiters and other planets.
In this project we will carry out a series of high resolution numerical simulations (using both Cartesian and spherical geometry), modelling the effects of magnetic fields upon the dynamics of the outer layers of a typical Hot Jupiter. In addition to the inclusion of magnetic fields, the key novel ingredient of these simulations is that they will include not only the radiative atmosphere of the planet, but also the upper layers of the (underlying) convective interior. The inclusion of both of these regions in these simulations will significantly enhance our understanding of heat transport in these outer layers, thus providing crucial new insights into the (long-standing) radius inflation problem.