Illustration of the NLFFF from the flux rope insertion model of van Ballegooijen (2004). Magnetic field constructed on September 20, 2013, 12:00 UT for (a) model 1 and (c) model 2. The solid-body rotation of the constructed NLFFF to September 24, 2013, 12:00 UT is shown for (b) model 1 and (d) model 2. In each plot the thin black lines denote the solar limb and the area of the high-resolution computational box, and the thick black lines denote field lines. The colour image illustrates the photospheric magnetic field distribution. Red and blue denote positive and negative flux.