Forces along a field line in the jet. Panel (a) shows the poloidal matter flux density as a background overplotted with poloidal magnetic field lines. The vectors show the total force along a representative field line originating from the disk at . Panel (b) plots the angular velocity Ω as the background. The vectors show the sum of the gravitational + centrifugal forces along the representative field line. Panel (c) shows the poloidal current as the background. The vectors show the total magnetic force along the representative field line.