FC at different evolutionary stages. Panel a: composite of the AIA 304 Å, 211 Å, and 171 Å images showing the filament eruption on 2020 Dec. 7. The white box shows the FOV of panels b–d. The black boxes 1 and 2 show the FOVs of the ONSET and NVST images as shown in Figs. 2b and 3, respectively. Panel b: HMI line-of-sight magnetogram with the main PIL indicated by the gold line. Panels c–d: composite of the AIA 304 Å and 171 Å images showing the remained FC and the confined filament eruption. The dashed line indicate the corresponding FC at different instants.