Oscillation detection and fitting. (a) Space-time map of Slit 1 near the apex of the loops in SJI 1400 are shown in Fig. 1. The negative intensity is shown in each map. These x − t maps show that the different rain clumps oscillate in phase at varying positions of the slits. The decay-less nature of transverse oscillations is also visible in the x − t maps. (b) The plus symbols mark the centers of the threads over-plotted with the obtained sinusoidal fits, which are represented by red curves. The oscillation properties are derived using sinusoidal fits.