Observations of the fishbone-like structure in AR 12297 on 2015 March 12. (a) Vertical component of the SDO/HMI vector magnetic field at 05:00:00 UT, showing an overview of AR 12297. (b) NVST TiO image taken at 05:53:30 UT. Labels “N1” and “N2” register the sunspots with negative polarity, while “P” denotes the sunspot with positive polarity. Label “p” indicates a narrow strip of positive polarity sandwiched between N1 and N2, located directly beneath the fishbone-like structure. (c) Composite AIA 171 Å (red), 193 Å (green), and 131 Å (blue) images show a typical ongoing brightening event. (d)–(f) IRIS/SJI 1330 Å, 1400 Å, and NVST Hα line center images displaying the general appearance of the fishbone-like structure. Iso-Gauss contours of ±200 G are superposed by white and blue curves in panel (e). The red dashed box outlines the field of view (FOV) in panels (b)–(c), and the blue one outlines the FOV in panels (d)–(f). (g) AIA 304 Å (red), 171 Å (black), and 193 Å (cyan) light curves extracted from the white dashed rectangle in panel (c). The vertical dashed line marks the time of the image shown in panel (c).