Letter to the Editor

Mesoscale flows in large aspect ratio simulations of turbulent compressible convection

Laboratoire d'Astrophysique de Toulouse-Tarbes, UMR CNRS 5572, Observatoire Midi-Pyrénées, 14 avenue É. Belin, 31400 Toulouse, France e-mail: rincon@ast.obs-mip.fr

Received: 23 August 2004
Accepted: 19 December 2004

Abstract

We present the results of a very large aspect ratio () numerical simulation of fully compressible turbulent convection in a polytropic atmosphere, and focus on the properties of large-scale flows. Mesoscale patterns dominate the turbulent energy spectrum. We show that these structures, which had already been observed in Boussinesq simulations by [CITE], have a genuine convective origin and do not result directly from collective interactions of the smaller scales of the flow, even though their growth is strongly affected by nonlinear transfers. If this result is relevant to the solar photosphere, it suggests that the dominant convective mode below the Sun's surface may be at mesoscales.