Thermohaline mixing in low-mass giants

TL;DR

This paper investigates thermohaline mixing in low-mass red giants, confirming its role in ^3He destruction, its occurrence mainly in stars under 1.5 solar masses, and its potential interaction with rotation and magnetic fields.

Contribution

It provides a detailed analysis of thermohaline mixing's occurrence, effects, and interactions in stars between 1 and 3 solar masses, highlighting its significance in stellar evolution.

Findings

Thermohaline mixing can destroy most ^3He in stars with initial mass less than ~1.5Msun.

Thermohaline mixing occurs during the red giant phase and can persist during core helium burning.

Interactions with rotation and magnetic fields may influence the mixing timescale.

Abstract

Thermohaline mixing has recently been proposed to occur in low mass red giants, with large consequences for the chemical yields of low mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1Msun and 3Msun, in comparison to other mixing processes acting in these stars. We confirm that thermohaline mixing has the potential to destroy most of the ^3He which is produced earlier on the main sequence during the red giant stage. In our models we find that this process is working only in stars with initial mass M <~ 1.5Msun. Moreover, we report that thermohaline mixing can be present during core helium burning and beyond in stars which still have a ^3He reservoir. While rotational and magnetic mixing is negligible compared to the thermohaline mixing in the relevant layers, the interaction of thermohaline motions with differential rotation and magnetic fields may be essential to establish the time scale of thermohaline mixing in red giants.