Double-diffusive mixing in stellar interiors in the presence of horizontal gradients

Abstract

We have identified an important source of mixing in stellar radiation zones, that would arise whenever two conditions are satisfied: (1) the presence of an inverse vertical compositional gradient, and (2) the presence of density-compensating horizontal gradients of temperature (alternatively, entropy) and composition. The former can be caused naturally by any off-center burning process, by atomic diffusion, or by surface accretion. The latter could be caused by rotation, tides, meridional flows, etc. The linear instability and its nonlinear development have been well-studied in the oceanographic context. It is known to drive the formation of stacks of fingering layers separated by diffusive interfaces, called intrusions. Using 3D numerical simulations of the process in the astrophysically-relevant region of parameter space, we find similar results, and demonstrate that the material transport in the intrusive regime can be highly enhanced compared with pure diffusion, even in systems which would otherwise be stable to fingering (thermohaline) convection.

Submitted to ApJ Letters

References in corpus (3)

• Thermohaline mixing: A physical mechanism governing the photospheric composition of low-mass giants
• Chemical Transport and Spontaneous Layer Formation in Fingering Convection in Astrophysics
• Transport by meridional circulations in solar-type stars

Cited by in corpus (6)

• On the Numerical Treatment and Dependence of Thermohaline Mixing in Red Giants
• A phenomenological modification of thermohaline mixing in globular cluster red giants
• The interaction between shear and fingering (thermohaline) convection
• Angular momentum transport, layering, and zonal jet formation by the GSF instability: nonlinear simulations at a general latitude
• Rotational mixing in carbon-enhanced metal-poor stars with s-process enrichment
• Influence of Rotation on Fingering Convection in Planetary Cores