The large scale distributions of gas, magnetic field and cosmic rays i
n the galactic halo are investigated. Our model is based on the analys
is of all-sky surveys of Hr gas (Leiden/Dwingeloo survey), soft X-ray
radiation (ROSAT all-sky survey), high energy gamma-ray emission (EGRE
T > 100 MeV), and radio-continuum emission (408 MHz survey). We found
a stable hydrostatic equilibrium configuration of the Galaxy which, on
large scales, is consistent with the observations. Instabilities due
to local pressure or temperature fluctuations can evolve only beyond a
scale height of 4 kpc. We have to distinguish 3 domains, with differe
nt physical properties and scale heights. 1) The gaseous halo has an e
xponential scale height h(z) similar or equal to 4.4 kpc. its radial d
istribution is characterised by a galactocentric scale length A(1) sim
ilar or equal to 15 kpc. On large scales all components of the halo -
gas, magnetic fields and cosmic rays - are in pressure equilibrium. Th
e global magnetic field is regularly ordered and oriented parallel to
the galactic plane. 2) The disk has a vertical scale height of about 0
.4 kpc. Characteristic for this region is the high gas pressure. The a
ssociated magnetic field is irregularly ordered and its equivalent pre
ssure is only similar or equal to 1/3 of the gas pressure. The cosmic
rays are decoupled from gas and magnetic fields. 3) The diffuse ionise
d gas layer with a vertical scale height of about 0.95 kpc and a radia
l scale length of Al - 15 kpc acts as a disk-halo interface. The magne
tic field in this region has properties similar to that in the disk. H
owever, here the cosmic rays ape coupled to the magnetic fields in con
trast to the situation within the galactic disk. The, gas pressure in
this transition region is essential for the stability of the galactic
halo system. Applying the model we can derive some major properties of
the Milky Way: Assuming that the distribution of the gas in the halo
traces the dark matter, we derive for a flat rotation curve a total ma
ss of M = 2.8 10(11) M.. The mass of the galactic halo is M-halo simil
ar or equal to 2.1 10(11) M.. We find that turbulent motions in the ga
seous halo can be described by the Kolmogoroff relation. The smallest
clouds, which are compatible with such a turbulent flow, are at temper
atures close to 3 K. They have linear sizes of similar to 20 au and ma
sses of similar to 2 10(-3) M.. A significant fraction of the galactic
dark matter may be in this form.