Magnetic reconnection between loops before the filament eruption observed by SDO/AIA: (a) AIA 304 Å, (b) 131 Å, (c) 171 Å, (d) 193 Å, (e) 211 Å, and (f) 335 Å images. The green solid arrows in (a)–(e) denote the current sheet. The cyan, green, and blue lines IJ, KL, and MN in (a) and (c) show the positions for time slices of AIA 304 Å and 171 Å images displayed in Figures 5(a), (b), and (d), respectively. The red and purple rectangles in (b) separately enclose the region for the DEM curve in Figure 5(e), and the location where the background emission is measured. In (c), the red pluses mark the positions between which the length of the current sheet is measured, the purple line denotes the position along which the width of the current sheet is calculated, and the red dotted lines outline loops L2 and L4. The blue rectangle in (e) marks the region for the light curves of the AIA EUV channels as shown in Figure 5(c). The FOV is denoted by the red rectangle in Figure 1(a). See Section 3.1 for details.