A model of rotating convection in stellar and planetary interiors: II -- gravito-inertial wave generation

TL;DR

This paper models gravito-inertial wave generation in rotating stellar and planetary interiors, analyzing how convection and interface properties influence wave excitation and energy flux, with implications for asteroseismology and internal dynamics.

Contribution

It introduces a monomodal convection model to quantify wave excitation mechanisms and their dependence on rotation and interface parameters in stellar and planetary interiors.

Findings

Sub-inertial waves can carry significant energy flux depending on Rossby number.

Super-inertial wave excitation is maximized near a Rossby number of unity.

Wave energy flux peaks near the lower cutoff frequency for certain Rossby numbers.

Abstract

Gravito-inertial waves are excited at the interface of convective and radiative regions and by the Reynolds stresses in the bulk of the convection zones of rotating stars and planets. Such waves have notable asteroseismic signatures in the frequency spectra of rotating stars, particularly among rapidly rotating early-type stars, which provides a means of probing their internal structure and dynamics. They can also transport angular momentum, chemical species, and energy from the excitation region to where they dissipate in radiative regions. To estimate the excitation and convective parameter dependence of the amplitude of those waves, a monomodal model for stellar and planetary convection as described in Paper I is employed, which provides the magnitude of the rms convective velocity as a function of rotation rate. With this convection model, two channels for wave driving are considered: excitation at a boundary between convectively stable and unstable regions and excitation due to Reynolds-stresses. Parameter regimes are found where the sub-inertial waves may carry a significant energy flux, depending upon the convective Rossby number, the interface stiffness, and the wave frequency. The super-inertial waves can also be enhanced, but only for convective Rossby numbers near unity. Interfacially excited waves have a peak energy flux near the lower cutoff frequency when the convective Rossby number of the flows that excite them are below a critical Rossby number that depends upon the stiffness of the interface, whereas that flux decreases when the convective Rossby number is larger than this critical Rossby number.