Ambipolar Drift in a Turbulent Medium

The interstellar magnetic field strength and density are observed to be correlated, but there is a large dispersion in this relation. In particular, the magnetic field is often observed to be weaker than expected. At low ionization fraction, ion-neutral drift, or ambipolar diffusion, permits slip of the field relative to the neutral gas and tends to make the field strength more uniform, but it is thought to be too slow to explain the observations. The purpose of this paper is to show that ion-neutral drift is significantly faster in a turbulent medium than in a quiescent one. We suggest that this fast ambipolar diffusion can explain the surprisingly low magnetic field strengths sometimes observed in dense interstellar gas.