Theories of convection and the spectrum of turbulence in the solar photosphere

Abstract

Classical theories of turbulence do not describe accurately inertial range scaling laws in turbulent convection and notably fail to model the shape of the turbulent spectrum of solar photospheric convection. To understand these discrepancies, a detailed study of scale-by-scale budgets in turbulent Rayleigh-Bénard convection is presented, with particular emphasis placed on anisotropy and inhomogeneity. A generalized Kolmogorov equation applying to convection is derived and its various terms are computed using numerical simulations of turbulent Boussinesq convection. The analysis of the isotropic part of the equation shows that the third-order velocity structure function is significantly affected by buoyancy forcing and large-scale inhomogeneities. Anisotropic contributions to this equation are also shown to be comparable to their isotropic counterpart at moderate to large scales. Implications of these results for convection in the solar photosphere, mesogranulation and supergranulation are discussed.

6 pages, 3 figures -- To appear in the Proceedings of Symposium no. 239 "Convection in Astrophysics", International Astronomical Union., held 21-25 August, 2006 in Prague, Czech Republic

References in corpus (4)

• Rayleigh and Prandtl number scaling in the bulk of Rayleigh-Benard turbulence
• Anisotropy, inhomogeneity and inertial range scalings in turbulent convection
• Mesoscale flows in large aspect ratio simulations of turbulent compressible convection
• Universality of anisotropic fluctuations from numerical simulations of turbulent flows