To reach these objectives, the project is structured around 2 tasks:
- Task I (TI): dynamical evolution of rotating magnetic stars;
- Task II (TII): tides and integrated evolution of stellar systems.
In TI, we have studied in a systematic way the physical mechanisms able to transport angular momentum in stellar radiation zones that drive the secular rotational and chemical evolutions of stars. They strongly impact the magnetism of stars and their interactions with their environment studied in TII.
First, we have done a complete study of the excitation, the propagation and the dissipation of gravito-inertial waves that propagate in stellar radiation zones because of buoyancy and rotation. We demonstrate that their stochastic convective excitation can be amplified in rapidly rotating stars and we explore their propagation for any stratification and rotation. We show that they trigger an important angular momentum transport that deeply modifies the evolution of stars. Next, we have studied the impact of rotation and viscous and heat diffusions on stellar convection. We show how rotation strongly impacts penetrative convection and thus chemical mixing. Third, we provide the first complete study of the anisotropic turbulent transport sustained by shear-induced instabilities in stellar radiation zones. For the first time we take into account coherently stable stratification, (differential) rotation and heat diffusion. We improve our understanding of star’s magnetism along their evolution thanks to new scaling laws for the amplitude of magnetic fields generated by dynamo action and their potential remnant fossil fields. Finally, we have developed a new generation of seismic diagnosis, which take into account (differential) rotation and realistic 3D magnetic topologies; they open a new window for constraining internal rotation, magnetism, and mixing in stars. New theoretical prescriptions and numerical scaling laws have been implemented in the code STAREVOL.
In TII, we have studied in a systematic way the variation of the dissipation of tidal inertial/gravity waves propagating in the convective envelope/radiative core of low-mass stars along their evolution. We have demonstrated that it varies over several orders of magnitude with stellar mass, age, metallicity, and rotation. The dissipation of tidal gravity waves dominates at the beginning of the pre-main-sequence and after the end of the main sequence; otherwise, the dissipation of tidal inertial modes dominates. Next, we have examined the complex interactions of tidal waves with differential rotation, rotating turbulent convection and magnetic fields.
In addition, we have studied tidal dissipation in every planetary type. First, we demonstrated how the mixing of heavy elements in the envelope of gaseous giant planets could enhance the dissipation. Next, we study the dissipation of atmospheric and oceanic tides in telluric planets. For instance, we demonstrated how the dissipation of atmospheric tides in convective layers near the ground leads to asynchronous planetary rotation. Using these results we have actively developed the ESPEM code, which takes into account tides, stellar winds, and MHD Star-Planet Interactions. We predict that the evolution of hot-Jupiter systems is driven by tidal interactions while the evolution of a super-Earth orbiting a M-dwarf is driven by MHD torques.
