  We simulated the million degree interstellar medium and its soft X-ray images
in the disk and halo of spiral galaxies using the bipolar hypershell (BHS)
model. In this model hourglass-shaped expanding shells of several kpc radii are
produced by a sudden energy release in the central region. We then applied our
model to a mini-sample of starburst galaxies seen under different inclinations
suhc as the nearly edge-on galaxies NGC 253. Our results reproduce the X-ray
characteristics observed in the 0.1--2.4 keV ROSAT energy band: The bipolar
hypershell morphology, the spectral energy distribution of the diffuse disk and
halo emission as well as absorption gaps in the diffuse X-ray emission caused
by a shadowing of soft X-rays due to cold intervening gas in the disks of the
galaxies. The required total energy for the starburst is estimated to be of the
order of $10^{55}$ ergs, corresponding to the overall kinetic energy generated
in $\sim 10^4$ type-II supernova explosions. The expansion velocity of the
shells is estimated to be $\sim 200$ \kms, which is necessary to heat the gas
to $\sim 0.2$ keV (2.3 million K), and the age to be of the order of $3 \times
10^7$ years. In the case of the very nearby galaxy NGC 253 all characteristics
of the BHS model can be studied with high spatial resolution. Using the
property that the shell morphology is sensitive to the ambient density
distribution, we propose using soft X-ray data to probe the gas distributions
in the disk, halo and intergalactic space. The application of our model to
images at higher spatial and spectral resolution, as provided by Chandra and
XMM, will help us to further disentangle the ISM density distributions and will
lead to a better understanding of the disk halo interface.
