Comparison between a potential field extrapolation (left column), the result of data driving using a driving cadence of Δt = 20δt (center column), and a nonlinear force free field extrapolation using the optimization code provided by Thomas Wiegelmann (right). The top and bottom rows show two different perspectives. The extrapolation time t = 1.55t _N is at courant step 380, near the end of the spheromak’s expansion.