THE HOT GAS FILLING FACTOR IN THE VICINITY OF THE SUN

With the help of a numerical code, we simultaneously follow the time evolution of a large number of supernova remnants and superbubbles in a stratified medium, and from there infer the filling factor of hot cavities near the Sun. We find that superbubbles give a much larger contribution than individual supernova remnants, particularly at high Galactic altitudes. Our derived hot gas filling factor is congruent-to 30% at the midplane and increases rapidly with height, reaching approximately 80%-90% at 2 kpc.