It is shown that a number of key observations of the Galactic ISM can be understood , if it is treated as a highly compressible and turbulent medium , energized predominantly by supernova explosions ( and stellar winds ) .
We have performed extensive numerical high resolution 3D hydrodynamical and magnetohydrodynamical simulations with adaptive mesh refinement over sufficiently long time scales to erase memory effects of the initial setup .
Our results show , in good agrement with observations , that ( i ) volume filling factors of the hot medium are modest ( typically below 20 % ) , ( ii ) global pressure is far from uniform due to supersonic ( and to some extent superalfvénic ) turbulence , ( iii ) a significant fraction of the mass ( \sim 60 % ) in the warm neutral medium is in the thermally unstable regime ( 500 < { T } < 5000 K ) , ( iv ) the average number density of O vi in absorption is 1.81 \times 10 ^ { -8 } { cm } ^ { -3 } , in excellent agreement with Copernicus and FUSE data , and its distribution is rather clumpy , consistent with its measured dispersion with distance .