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

(1) The small-scale downflows generated in the near-surface layer penetrate into deeper layers to some extent and excite small-scale turbulence in the region >0.9 R, where R is the solar radius. (2) In the deeper convection zone (<0.9 R), the convection is not influenced by the location of the upper boundary. (3) Using a large eddy simulation approach, we can achieve small-scale dynamo action and maintain a field of about 0.15B eq-0.25B eq throughout the convection zone, where B eq is the equipartition magnetic field to the kinetic energy.

(4) The overall dynamo efficiency varies significantly in the convection zone as a consequence of the downward directed Poynting flux and the depth variation of the intrinsic convective scales.