Various components that determine the drift velocity u_amb, calculated for Experiment 2. Left column: ratio |B|²/ρ². Middle column: maps of . Right column: inverse of the characteristic length of the magnetic field, only in places where η_amb >  10¹³ cm² s⁻¹. Two isocontours for η_amb are superimposed in the left and middle column panels as green lines (10¹³ cm² s⁻¹) and blue lines (10¹⁵ cm² s⁻¹). The velocity field due to the ambipolar diffusion u_amb (see Eq. (14)) is also shown in those two columns with red arrows only in regions where η_amb >  10¹³ cm² s⁻¹. Additionally, dashed lines indicate the location of the solar surface (line at z = 0 Mm) and of the transition region (isocontour at T = 10⁵ K). An animation of this figure is available online.