2017/11/16 by Y. Bekki, H. Hotta, T. Yokoyama
Engineering · Physics and Astronomy · #Amplitude #Convection #Convection cell #Convection zone #Convective heat transfer #Convective inhibition #Fluid Dynamics and Turbulent Flows #Fluid dynamics and aerodynamics studies #Prandtl number #Solar and Space Plasma Dynamics #Thermal #Thermal diffusivity #astro-ph.SR
paper · pdf · doi:10.3847/1538-4357/aa9b7f
17 pages, 13 figures, accepted for publication in ApJ
arxiv created 2017/11/16 · openalex created_date 2017/12/04 · openalex publication_date 2017/12/14 · arxiv updated 2017/12/27 · openalex updated_date 2026/08/05
Abstract It has recently been recognized that the convective velocities achieved in current solar convection simulations might be overestimated. The newly revealed effects of the prevailing small-scale magnetic field within the convection zone may offer possible solutions to this problem. The small-scale magnetic fields can reduce the convective amplitude of small-scale motions through the Lorentz-force feedback, which concurrently inhibits the turbulent mixing of entropy between upflows and downflows. As a result, the effective Prandtl number may exceed unity inside the solar convection zone. In this paper, we propose and numerically confirm a possible suppression mechanism of convective velocity in the effectively high-Prandtl number regime. If the effective horizontal thermal diffusivity decreases (the Prandtl number accordingly increases), the subadiabatic layer which is formed near the base of the convection zone by continuous depositions of low entropy transported by adiabatically downflowing plumes is enhanced and extended. The global convective amplitude in the high-Prandtl thermal convection is thus reduced, especially in the lower part of the convection zone via the change in the mean entropy profile, which becomes more subadiabatic near the base and less superadiabatic in the bulk.