EVOLUTION OF SUPERNOVA REMNANT BUBBLES IN A WARM DIFFUSE MEDIUM - SURVEY OF RESULTS FROM ONE-DIMENSIONAL MODELS AND THEIR IMPACT ON ESTIMATES OF INTERSTELLAR POROSITY

With straightforward modeling of the late evolution of supernova remnants, including a modest nonthermal contribution to the pressure in the preshock (ambient) gas, we demonstrate that in the solar neighborhood: 1. the porosity induced by the remnant population in a warm intercloud medium (n is similar to 0.15 cm-3) would not be large (q less than or similar to 0.2), and 2. the slowly cooling supernova remnant bubbles harbor large populations of the high-stage ions (O VI, N V, and C IV at least), sufficient to explain their mean densities in the galactic plane (though a comparable contribution may derive from OB association bubbles). With these results it is no longer clear that there is any need for a pervasive phase of hot ps in the interstellar medium, beyond that found within localized disturbances.