Gas pressure P_g, 0 (upper panel, left) at the inner boundary (z₀ = 1 kpc) for Model W (full line) and Model H (dashed line) as seen over a time interval of 10⁸ years for the case when mass and energy losses are included. The CR pressure P_c, 0 (upper panel, right) is about a factor of 10 less than the gas pressure (note the change of scale). The decrease of the mass loss rate Ṁ₀ (lower panel, left) occurs already 10 × 10⁶ yr after the SNe have triggered an outflow. After this time the galactic wind changes its nature as inferred from the decreasing values of the outflow velocity u₀ (lower panel, right).