Tidal dissipation in stars and planets: simulations from first principles

Many extrasolar planets orbit their stars in only a few Earth days. At such close distances, gravitational tidal interactions can play an important role in modifying planetary orbits and stellar and planetary spins. The timescales for these evolutionary processes depend on how efficiently the kinetic energy of tidal flows is dissipated inside stars and planets, but this is not well understood theoretically. This project is computational in nature and will involve first principles numerical simulations, employing state-of-the-art algorithms on high-performance computers, to explore the mechanisms of tidal dissipation in the fluid layers of stars and planets. In particular, I propose to investigate the interaction between tidal flows and turbulent convective flows in rotating stars, and the mechanisms that lead to alignment of the stellar (and planetary) spin and the planetary orbit. The results from these simulations will be used to interpret astrophysical observations and to make predictions, for example, of the rotation rates of planet-hosting stars, and of possible orbital decay of the shortest-period planets that transit in front of their stars. These predictions can be tested by future observations using e.g. SuperWASP, NGTS, CHEOPS, TESS and PLATO.

The study of extrasolar planetary systems, and its relation to the possibility of life existing elsewhere in the Universe, has a significant cultural impact. More generally, the British public has a great deal of interest in astronomy, as evidenced by the more than 200 amateur astronomical societies. I propose to give talks to local astronomy societies, where I will endeavour to convey the many exciting observational advances in the field of extrasolar planets over the past two decades, along with some of my research results. I will also give talks in local schools, to students between the ages of 11 and 18, incorporating some of my research interests into the talks. This is a very important means of inspiring the next generation of scientists.

STFC recognises three ways of maximising the impact of its investment for the benefit of the United Kingdom and its people - world-class research, world-class innovation and world-class skills. This project, and the research undertaken in the group, qualifies on all three counts, in terms of the astrophysical research itself, the possible innovation of fundamentally new numerical methods (which may also be useful in areas outside astrophysics), and the training of Postdocs and PhD students in utilising high-performance computing skills (which are enormously useful in many areas outside astrophysics).