Ambipolar drift heating in turbulent molecular clouds

We present calculations of frictional heating by ion-neutral drift in three -dimensional simulations of turbulent, magnetized molecular clouds. We show that ambipolar drift heating is a strong function of position in a turbule nt cloud, and its average value can be significantly larger than the averag e cosmic-ray heating rate. The heating rate per unit volume due to ambipola r drift, H-AD = \J x B\(2)/rho(t)nu(ln) similar to B-4/(16 pi(2)L(B)(2)rho( i)nu(in)), is found to depend on the rms Alfvenic Mach number, M-A,, and on the average field strength, as H-AD proportional to M-2(A)<\ B \>(4) This implies that the typical scale of variation of the magnetic field, L-B, is inversely proportional to M-A, which we also demonstrate.