Trace of the oscillations in the filament for the first event on February 5, 2015, observed with AIA 171 Å and Hα. Panel a: filament seen in absorption in AIA 171 Å on February 5, 2015, with the artificial slit used to construct the time–distance diagrams (panels b-d) shown as a white contour. Panel b: time–distance diagram for the AIA171 image along the topmost 150″ of the slit; panel b in Fig. 3, taken at time 20:50 UT. Panels c and d contain the time–distance diagrams for the brightness along the curved slit, clearly showing the oscillatory patterns analysed in this paper. The white tracks in panels c and d show one of the fits obtained for the oscillation, which has a period of 77 min, velocity amplitude of 33 km s⁻¹, and a damping time of τ = 196 min. The black vertical stripes in panels b, c, and d are data gaps.