Mach Number Dependence of Turbulent Magnetic Field Amplification:
  Solenoidal versus Compressive Flows
  We study the growth rate and saturation level of the turbulent dynamo in
magnetohydrodynamical simulations of turbulence, driven with solenoidal
(divergence-free) or compressive (curl-free) forcing. For models with Mach
numbers ranging from 0.02 to 20, we find significantly different magnetic field
geometries, amplification rates, and saturation levels, decreasing strongly at
the transition from subsonic to supersonic flows, due to the development of
shocks. Both extreme types of turbulent forcing drive the dynamo, but
solenoidal forcing is more efficient, because it produces more vorticity.
