(a–e) Formation of a flux rope over the external PIL through the photospheric effects of surface diffusion and differential rotation. The images are shown on (a) day 3, (b) day 22, (c) day 35, (d) day 40, and (e) day 42. For (a, b) the flux values saturate at ±5 G, and for (c–e) ±2 G. (f) Example of the inverse‐﹩\textsf{S}﹩–shaped flux ropes formed over the internal PIL of the trailing bipole on day 18.