The shearing motion, the flux cancellation, and the emerging dipole in AR 13842 prior to the eruption. Panels (a1)–(a3), (b1)–(b2), and (c1)–(c3): the SDO/HMI LOS magnetograms. The blue square in panel (a1) outlines the FOVs in panels (a2)–(a3), (b1)–(b2), (c1)–(c3), and Figures 3(a1)–(a5). The solid lines in panels (a1)–(a3) denote the PIL of the AR core region, and the red arrows in panels (a2)–(a3) represent the horizontal velocities obtained by the DAVE method. The areas “1”–“3” in panel (b1) and “4”–“6” in panel (c2) outline the locations where the flux cancellation happened. Panel (b3) shows the time evolution of the magnetic flux within the cyan solid curves in panels (b1)–(b2). The red solid curve in panel (c1) labels an emerging dipole. An animation of the HMI/LOS magnetograms from 2024 October 2 00:08:46 UT to 2024 October 3 12:03:30 UT, showing the evolution of photospheric magnetic fields in AR 13842 before the eruption, is available. In this animation, the cyan, orange, green, purple, blue, and red curves outline the cancellation areas “1”–“6,” respectively, which correspond to the labeled areas in panels (b1) and (c2). The obvious cancellation within areas “1”–“6” took place from 2024 October 2 02:44 UT to 2024 October 2 05:40 UT, from 2024 October 2 04:02 UT to 2024 October 2 12:49 UT, from 2024 October 2 22:05 UT to 2024 October 3 02:38 UT, from 2024 October 3 02:57 UT to 2024 October 3 06:51 UT, from 2024 October 3 08:09 UT to 2024 October 3 12:02 UT, and from 2024 October 3 10:45 UT to 2024 October 3 12:02 UT, separately. The duration of this animation is 9 s.

(An animation of this figure is available in the online article.)

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.