Thickness distributions of runs A0 and B0 at time t = 5 × 10^-3. Black lines correspond to the ideal MHD runs and red lines to the runs with ambipolar diffusion. The corresponding dashed lines show the 1024³ cases. Above, threshold 2000 cm^-3 for filament identification, below, threshold of 5000 cm^-3. The dotted lines indicate the mean ambipolar diffusion dissipation length λ_d, calculated from Eq. (1) for each density threshold, the resolution lengths l_m,512 and l_m,1024, equal to the length of 20 cells, and the sonic length l_s, defined by Eq. (11), for an rms Mach number of 5.