Sketch of the initial configuration adopted for the galactic wind models. The SB is approximated by a Kompaneets solution until break-out, where z₀ = 1 kpc fixes the location of the inner boundary conditions of the flux tube. All physical variables depend on time t and on the distance from the Galactic plane z. The gravitational acceleration g(z, R₀) also depends on R₀, the Galactocentric distance of the flux tube (see text for more details).