We present the results of a very large aspect ratio ( A = 42.6 ) 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 , 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 .