Structure of Convection and Magnetic Field Without Rotation

Abstract

Using the developed numerical code, we perform non-rotating high-resolution calculations of solar global convection, which resolve convective scales of less than 10 Mm. The main conclusions of this study are the following. (1) The small-scale downflows generated in the near surface layer penetrate down to deeper layers and excite small-scale turbulence in the region of $>$ $0.9R_\odot$, where $R_\odot$ is the solar radius. (2) In the deeper convection zone ($<$ $0.9R_\odot$), the convection is not affected by the location of the upper boundary. (3) Using an LES (Large Eddy Simulation) approach we achieved small-scale dynamo action and maintained a field of $0.15-0.25B_\mathrm {eq}$ throughout the convection zone, where $B_\mathrm {eq}$ is the equipartition magnetic field to the kinetic energy. (4) The overall dynamo efficiency significantly varies in the convection zone as a consequence of the downward directed Poynting flux and the depth variation in the intrinsic convective scales. For a fixed numerical resolution the dynamo relevant scales are better resolved in the deeper convection zone and are therefore less affected by numerical diffusivity, i.e. the effective Reynolds numbers are larger.