Multiwavelength imaging observations on the AR filament. Panel a: corresponding Hα image of the filament provided by the Kanzelhöhe Observatory at 13:10:46 UT, where the red and blue contour lines represent different levels of magnetic field strength ranging from −50 G to 50 G. The arrow indicates a right-bearing barb of the filament. Panel b: SDO/AIA 304 Å image observed at 13:10:43 UT. Panel c: SDO/AIA 171 Å image observed at 23:19:36 UT. The arrows mark left-skewed flare loops formed after the filament eruption.