  We study the growth of small fluctuations of magnetic field in supersonic
turbulence, the small-scale dynamo. The growth is due to the fastest turbulent
eddies above the resistive scale. We observe that for supersonic turbulence
these eddies are effectively incompressible which creates a robust structure of
the growth. The eddies are localised below the sonic scale $l_s$ defined as the
scale where the typical velocity of the turbulent eddies equals the speed of
sound. Thus the flow below $l_s$ is effectively incompressible and the field
growth proceeds as in incompressible flow. At large Mach numbers $l_s$ is much
smaller than the integral scale of turbulence so the fastest growing mode of
the magnetic field belongs to small-scale turbulence. We derive this mode and
the associated growth rate numerically in a white noise in time model of
turbulence. The relevance of this model relies on considering evolution time
larger than the correlation time of turbulence.
