Time series of magnetograms showing the evolution of the line‐of‐sight magnetic field as observed by the Hinode SOT with the NFI at 4 hr intervals prior to the X3.4 flare. Coordinates (with north up and—by solar physics convention—west toward the right) are in pixels of 0.16^{﹩\arcsec﹩} each; the area shown covers the central 10% of the footprint of the NLFF field model volume (compare the smallest square in Fig. 1a to its full field of view). Note that the NFI magnetograph signal is nonmonotonic, disappearing in the umbrae of the two spots. Panel (d) shows in red the brightest segments of the flare ribbons seen in the Ca II H channel at 02:16:39 UT (cf. Fig. 1b); it also outlines the brightest quiescent kernel in soft X‐rays seen by the Hinode XRT at the same time (green contour) and the brightest coronal structure (black contour; cf. Fig. 1a). The latter two are repeated in (c), taken close to the time of the preflare vector magnetogram obtained by the spectropolarimeter. The magnetic information in that panel has been replaced by the line‐of‐sight integral of the vector norm of the electrical currents (cf. Fig. 4a) within the blue contour, which is where these currents are strongest. This figure is also available as mpeg animations movie1.mpg and movie2.mpg.