Angular momentum transport by internal waves in the solar interior

TL;DR

This paper investigates how low-frequency internal gravity waves in the solar interior can efficiently transport angular momentum, potentially explaining the observed flat rotation profile of the Sun.

Contribution

It provides a simplified model for angular momentum transport by internal waves, highlighting their significant role in solar rotation dynamics.

Findings

Transport operates on a timescale of about 10^7 years.

It likely explains the flat rotation profile observed in the Sun.

The efficiency of wave-driven transport is relatively high.

Abstract

The internal gravity waves of low frequency which are emitted at the base of the solar convection zone are able to extract angular momentum from the radiative interior. We evaluate this transport with some simplifying assumptions: we ignore the Coriolis force, approximate the spectrum of turbulent convection by the Kolmogorov law, and couple this turbulence to the internal waves through their pressure fluctuations, following Press (1981) and Garcia Lopez & Spruit (1991). The local frequency of an internal wave varies with depth in a differentially rotating star, and it can vanish at some location, thus leading to enhanced damping (Goldreich & Nicholson 1989). It is this dissipation mechanism only that we take into account in the exchange of momentum between waves and stellar rotation. The flux of angular momentum is then an implicit function of depth, involving the local rotation rate and an integral representing the cumulative effect of radiative dissipation. We find that the efficiency of this transport process is rather high: it operates on a timescale of 10^7 years, and is probably responsible for the flat rotation profile which has been detected through helioseismology.