Estimation of turbulent diffusivity with direct numerical simulation of stellar convection

Abstract

We investigate the value of horizontal turbulent diffusivity η by numerical calculation of thermal convection. In this study, we introduce a new method whereby the turbulent diffusivity is estimated by monitoring the time devel- opment of the passive scalar, which is initially distributed in a given Gaussian function with a spatial scale d0. Our conclusions are as follows: (1) Assuming the relation η = Lcvrms/3 where vrms is the RMS velocity, the characteristic length Lc is restricted by the shortest one among the pressure (density) scale height and the region depth. (2) The value of turbulent diffusivity becomes greater with the larger initial distribution scale d0. (3) The approximation of turbulent diffusion holds better when the ratio of the initial distribution scale d0 to the characteristic length Lc is larger.

18 pages, 4 figures, 1 table, accepted to ApJL

References in corpus (8)

• Predicting solar cycle 24 with a solar dynamo model
• Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport Dynamics and Persistence of Memory in Advection versus Diffusion Dominated Solar Convection Zones
• Turbulent magnetic Prandtl number and magnetic diffusivity quenching from simulations
• Alpha effect and turbulent diffusion from convection
• Numerical Calculation of Convection with Reduced Speed of Sound Technique
• Origin of solar torsional oscillations
• Decay of a simulated mixed-polarity magnetic field in the solar surface layers
• The dual role of shear in large-scale dynamos

Cited by in corpus (4)

• Numerical simulations of active region scale flux emergence: From spot formation to decay
• High-resolution calculation of the solar global convection with the reduced speed of sound technique: II. Near surface shear layer with the rotation
• High-resolution calculations of the solar global convection with the reduced speed of sound technique: I. The structure of the convection and the magnetic field without the rotation
• Lorentz force mediation of turbulent dynamo transitions