SOLAR CONVECTION - COMPARISON OF NUMERICAL SIMULATIONS AND MIXING-LENGTH THEORY

We compare the results of realistic numerical simulations of convectio n in the superadiabatic layer near the solar surface with the predicti ons of mixing-length theory. We find that the peak values of such quan tities as the temperature gradient, the temperature fluctuations, and the velocity fluctuations, as well as the entropy jump in the simulati on, can be reproduced by mixing-length theory for a ratio of mixing le ngth to pressure scale height alpha approximate to 1.5. However, local mixing-length theory neither reproduces the profiles of these variabl es with depth nor allows penetration of convective motions into the ov erlying stable photosphere.