Astro Seminar: Tidal dissipation due to the interactions of the precessional instability and convection

Tidal dissipation in star-planet systems can occur through a myriad of mechanisms, one of which is the precessional instability. This instability acts on the precessional flows in rotating fluid planets and stars whose spin and orbital axes are misaligned, exciting inertial waves. We have studied its interaction with rotating convection in a local Cartesian model, attempting to constrain the contributions of both the precessional instability and convection to tidal dissipation. If the driving of the precessional instability is sufficiently strong a continuously turbulent flow is observed, with associated continuous tidal dissipation. Convective motions also act as a turbulent viscosity on large-scale tidal flows, resulting in continuous tidal dissipation. We observe that the presence of precession also enhances the vertical velocities and Nusselt numbers compared to those of the purely convective case. Furthermore, we find that stronger convective driving increases the tidal dissipation due to the turbulent viscosity, whilst reducing the tidal dissipation due to the precessional instability. We derive and subsequently evaluate our scaling laws using interior models of Hot Jupiters computed with MESA. We estimate that 1) the precessional instability is efficient to align the spin and orbit of short-period Hot Jupiters and 2) the tidal dissipation due to the turbulent viscosity is negligible in giant planets compared to the tidal dissipation due to inertial wave mechanisms.