Disc-halo interaction - I. Three-dimensional evolution of the Galactic disc

The results of a three-dimensional model for disc-halo interaction are pres ented here. The model considers explicitly the input of energy and mass by isolated and correlated supernovae in the disc. Once disrupted by the explo sions, the disc never returns to its initial state. Instead it approaches a state where a thin H I disc is formed in the Galactic plane, overlaid by t hick H I and H II gas discs with scaleheights of 500 pc and 1-1.5 kpc, resp ectively. The upper parts of the thick H II disc (the diffuse ionized mediu m) act as a disc-halo interface, and its formation and stability are direct ly correlated to the supernova rate per unit area in the simulated disc.