Core-envelope coupling of gravito-inertial waves in pre-main-sequence solar-type stars

The recent detection of solar equatorial Rossby waves has renewed interest in the study of gravito-inertial waves propagating in the convective envelope of solar-type stars. In particular, the ability of these envelope gravito-inertial modes to couple with those trapped in the radiative interior could open up new opportunities for probing the deep-layer dynamics of solar-type stars. The possibility for such a coupling to occur is particularly favoured among pre-main-sequence (PMS) solar-type stars. Indeed, due to the contraction of the protostellar object, they are able to reach high rotation frequencies before nuclear reactions are ignited and magnetic braking becomes the driving mechanism for their rotational evolution. In this work, we studied the coupling between the envelope inertial waves and the radiative interior g modes in PMS stars, focussing on the case of prograde dipolar modes. We considered the cases of 0.5 M⊙ and 1 M⊙ PMS models, each with three different scenarios of rotational evolution. We show that for stars that have formed with a sufficient amount of angular momentum, this coupling can occur in frequency ranges that are accessible to space-borne photometry, creating inertial dips in the period spacing pattern. Using an asymptotic analysis, we characterised the shape of these inertial dips to show that they depend on rotation and on the stiffness of the convective-radiative interface.