Modeling stellar convective transport with plumes through the non-equilibrium effect

Abstract

By reckoning the plume as the coherent fluctuation, a transport model for the convective turbulence is constructed with the aid of the nonequilibrium effect along plume motions, and applied to a stellar convective flow. One of the prominent characteristics of a surface cooling-driven convection, the enhanced and localized turbulent mass flux below the surface layer, which cannot be reproduced at all by the usual eddy-diffusivity model with mixing length theory (MLT), is well reproduced by the present model with the non-equilibrium effect. Our results show that the incorporation of plume motion into turbulent transport model through the non-equilibrium effect is an important and very relevant extension of mean-field theory beyond the heuristic gradient transport model with MLT.