Panels a–b: AIA 171 and 304 Å images at 07:00 UT. The arrows point to the long filament. Panel c: HMI LOS magnetogram at 06:59 UT. The arrow points to AR 11112. Panel d: GONG Hα image at 10:55:34 UT. “EP” and “WP” represent the eastern and western parts of the filament, respectively. In panel a a slice (S1) is selected to investigate the longitudinal oscillations of EP, whose time-distance diagram is shown in Fig. 10. The red, cyan, and orange circles indicate the oscillating threads (thd_a, thd_b, and thd_c) in EP. In panel d a slice (S2) is selected to investigate the evolution of WP, whose time-distance diagram is shown in Fig. 5.