Inhomogeneous model of the photosphere

A new method for the construction of empirical models of photosphere is developed starting with a first approximation called ‘multicolumn’. The old idea of two or three column models is thus kept but completed by the following ideas: - A good photograph of granulation is a fair representation of topological features along x and y. - Vertical distributions T(z), P(z) cannot be very much different from distributions given by stellar atmosphere models in radiative and hydrostatic equilibrium. The sampling interval (200 km) is such that a ‘granule’ is represented by 10 to 30 columns. Horizontal transfer is computed explicitly at each point. Corrections are introduced in the model but are not of significant importance: temperature differences of 1000 K or more at the same geometrical depth in the τ = 1 region are compatible with a life time of the order of 10 min. The importance of pressure is emphasized: significant pressure excess in the granule is suggested a priori. Results tend to confirm this hypothesis.