Impact of large-scale magnetic fields on stellar structure and evolution

We Study the impact on the stellar structure of a large-scale magnetic field in stellar radiation zones. The field is in magneto-hydrostatic (MHS) equilibrium and has a, non force-free character, which allows us to study it's influence both on the mechanical and and on the energetic balances. This approach is illustrated in the case of an A(p) star where the magnetic field matches at the surface with in external potential one. Perturbations of the stellar structure are semi-analytically computed. The relative importance of the magnetic physical quantities is discussed and a hierarchy, aiming at distinguishing various refinement degrees in the implementation of a large-scale magnetic field in a stellar evolution code, is established. This treatment also allows us to deduce the gravitational multipolar moments and the change in effective temperature associated with the presence of a magnetic field.