  We study the effects of ambipolar diffusion (AD) on hydromagnetic turbulence.
In most of the cases, we use the single fluid approximation where the drift
velocity between charged and neutral particles is proportional to the Lorentz
force. In two cases we also compare with the corresponding two-fluid model,
where ionization and recombination are included in the continuity and momentum
equations for the neutral and charged species. We consider the regime of large
magnetic Prandtl number, relevant to the interstellar medium. The magnetic
field properties are found to be well represented by the single fluid
approximation. We quantify the effects of AD on total and spectral kinetic and
magnetic energies, the Ohmic and AD dissipation rates, the statistics of the
magnetic field, the current density, and the linear polarization as measured by
the rotationally invariant E and B mode polarizations. We show that the
kurtosis of the magnetic field decreases with increasing AD. The E mode
polarization changes its skewness from positive values for small AD to negative
ones for large AD. Even when AD is weak, changes in AD have a marked effect on
the skewness and kurtosis of E, and only a weak effect on those of B. These
results open the possibility of employing E and B mode polarizations as
diagnostic tools for characterizing turbulent properties of the interstellar
medium.
