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Stars are dynamical rotating, magnetic, turbulent objects. Breakthroughs are now obtained for our knowledge of their internal dynamics thanks to observational constraints obtained by high-precision helio- and asteroseismology for the Sun and stars respectively. Indeed, observed internal rotation profiles show that they are the seats of strong and efficient angular momentum transport mechanisms all along their evolution from their birth to their death. To explain these observations, two mechanisms in convectively stable stellar radiation regions, which drive the secular rotational evolution of stars, are proposed: internal gravity waves, magnetic fields and their interactions with differential rotation, large-scale meridional flows and turbulence (e.g. Talon & Charbonnel 2005; Strugarek, Brun & Zahn 2011). These mechanisms deeply impact the evolution of stars, which have a broad impact on their planetary and galactic environment.
The main objective of this PhD project is to build realistic modelling of internal angular momentum transport mechanisms in stars using synergies between advanced semi-analytic methods devoted to the study of the impact of dynamical processes on secular time scales and of 3D ASH numerical simulations computed on High Performance Computing large facilities (CCRT) which allow us to study 3D and nonlinear MHD mechanisms in stars. New 2D secular equations, ab-initio scaling laws and prescriptions will be obtained. A peculiar effort will be done for the study of internal gravity waves, driven by the restoring buoyancy force, modified simultaneously by differential rotation and magnetism (also called magneto-gravito-inertial waves), which are excited by turbulent convective motions at radiation/convection interfaces, and on their breaking. It will benefit of our recent advances obtained simultaneously thanks to global 3D nonlinear ASH simulations of the Sun (Brun, Miesch & Toomre 2011; Alvan, Brun & Mathis 2014) and of 3D asymptotic theoretical models allowing their detailed analysis (Alvan et al. 2015). This allowed us to compute waves spectrum, amplitude, damping and visibility. However, these studies should now be generalized in a systematic way for all low mass and intermediate-mass stars (from K to A type stars) all along their evolution (e.g. Browning, Brun & Toomre 2004; Fuller et al. 2014; Lee, Neiner & Mathis 2014). In this framework, it will be necessary to characterize waves dynamics for all possible stratification, rotation, shear and magnetic field intensity (e.g. Mathis & de Brye 2012; Mathis, Neiner & Tran Minh 2014) to compute their spectrum, amplitude, damping, visibility and induced transport of angular momentum. This work will allow us to give scaling laws and parameters diagram mandatory to interpret current and future helio- and asteroseismic data (SOHO, CoRoT, Kepler/K2 and TESS & PLATO) to obtain a general understanding of the dynamical evolution of stars. This PhD project is part of the ERC project SPIRE (Stars: Dynamical Processes driving tidal Interactions, Rotation and Evolution; PI: S. Mathis).
Alvan, Brun & Mathis 2014, A&A, 565, 42
Alvan, Strugarek, Brun, Mathis & Garcia 2015, A&A, 581, 112
Brun, Miesh & Toomre 2011, ApJ, 742, 79
Browning, Brun & Toomre 2004, ApJ, 601, 512
Fuller et al. 2014, ApJ, 796, 17
Lee, Neiner & Mathis 2014, MNRAS, 443, 1515
Mathis & de Brye 2012, A&A, 540, 37
Mathis, Neiner & Tran Minh 2014, A&A, 565, 47
Strugarek, Brun & Zahn 2011, A&A, 532, 34
Talon & Charbonnel 2005, A&A, 440, 981