Description
The flux from a radiating surface depends significantly on the opacity and its functional dependence on temperature. This is why the correct depth of the convection zone was only known since the discovery of the H-minus opacity by Wildt (1938). This leads to the concept of convection driven by cooling from above rather than heating from below, which is sometimes also called entropy rain. An important feature is that the enthalpy flux cannot be modeled solely by the superadiabatic gradient, but there is also the Deardorff term that carries enthalpy outward. This contribution can also lead to weakly subadiabatic convection and may be responsible for convection on length scales smaller than the local scale height
