FIGURE F.4 A magnetic confinement concept such as the reversed-field pinch (RFP) (top) is a relatively self-organizing configuration that is subject to turbulent magnetic field structures. The magnetic topology includes a reversal of the toroidal field inside the plasma owing to plasma currents. Under normal inductive current drive, the magnetic field lines can readily become chaotic, as indicated by a puncture plot of the field lines as they traverse a poloidal plane (bottom left). With finer control of the plasma currents, well-defined flux surfaces are restored (bottom right). NOTE: BT, toroidal magnetic field; BP, poloidal magnetic field. Courtesy of S.C. Prager, University of Wisconsin at Madison.