Diffusion of a trace element in anisotropic radiative hydrodynamic turbulence

We consider the problem of trace elements diffusion in parts of radiative envelopes where radiative transfer is not negligible, i.e. viscosity is mainly due to an exchange of momentum between photons and ions and when one has local thermodynamical equilibrium. The flow is made anisotropic by an external shear that mimics the effect of meridional circulation. Although the photons are nearly thermalized, the radiation field is not isotropic because there is an external flux of radiation in the radial (here vertical) direction The tracer is then released into the flow and we study how the anisotropy of turbulence breaks the diffusion of a trace element.