Nonlinear Mixing driven by Internal Gravity Waves

TL;DR

This paper derives the fundamental non-linear mixing effects caused by internal gravity waves in stratified fluids, highlighting their dependence on wave velocity, stratification, and diffusivities, with implications for stellar interior modeling.

Contribution

It provides the first quantitative derivation of non-linear wave mixing in stratified fluids from first principles, considering thermal and compositional effects.

Findings

Mixing scales as the fourth power of wave velocity

Stratification suppresses wave mixing

Diffusivities influence the mixing process

Abstract

Hydrodynamic waves propagate through stellar interiors, transporting energy and angular momentum. They can also advect fluid elements to produce mixing, but this effect has not been quantified from first principles. We derive the leading order non-linear wave mixing due to internal gravity waves in a thermally and compositionally-stratified fluid. We find that this scales as the fourth power of wave velocity, that it is suppressed by compositional stratification, and that it depends on the thermal and compositional diffusivities.