MERCREDI 1 AVRIL 2009 14 heures Salle Séminaire 5 Centre de Physique Théorique Marseille-Luminy Alain Brizard St-Michael College, Colchester, Vermont, USA Title: Ray phase-space methods in linear mode conversion Abstract: A three-wave Budden model with two resonance layers is constructed that allows recirculation of energy fluxes along a quadrangle in ray phase space. The transmission, reflection, and conversion coefficients for this extended Budden problem are calculated by ray phase-space methods and the modular-eikonal approach. Analytical and numerical results show that all coefficients exhibit interference effects that depend on an interference phase calculated from the coupling constants and the area enclosed by the quadrangle.