Gravito-inertial modes in a differentially rotating spherical shell

TL;DR

This study investigates how differential rotation affects gravito-inertial oscillation modes in a star's radiative zone, revealing complex propagation behaviors and mode localization patterns.

Contribution

It provides the first detailed analysis of axisymmetric gravito-inertial modes in a differentially rotating stellar model using spectral methods.

Findings

Modes can propagate throughout the shell or be confined to subdomains.

Some modes concentrate energy around shear layers called attractors.

Propagation domain geometries influence mode visibility.

Abstract

While many intermediate- and high-mass main sequence stars are rapidly and differentially rotating, the effects of rotation on oscillation modes are poorly known. In this communication we present a first study of axisymmetric gravito-inertial modes in the radiative zone of a differentially rotating star. We consider a simplified model where the radiative zone of the star is a linearly stratified rotating fluid within a spherical shell, with differential rotation due to baroclinic effects. We solve the eigenvalue problem with high-resolution spectral computations and determine the propagation domain of the waves through the theory of characteristics. We explore the propagation properties of two kinds of modes: those that can propagate in the entire shell and those that are restricted to a subdomain. Some of the modes that we find concentrate kinetic energy around short-period shear layers known as attractors. We describe various geometries for the propagation domains, conditioning the surface visibility of the corresponding modes.