Random combination of spherical harmonics up to degree 5 represent the brilliance over the stellar disk. Left panel: graphical definition of the coordinates of the blue square over the disk. Right panel: brilliance of the disk along that particular radius in the left image. The vertical arrows indicate the vertical, radial, velocity included in the model to represent the emerging plasma velocity. We note that the zero velocity is shifted so that all velocities are positive. The red horizontal arrows represent the velocities of advection of the plasma towards the cold, integranular regions where it sinks down into the stellar interior. These horizontal velocities are not included in the actual model.