Generation and propagation of a prominence spicule. Panel a: intensity vs. time at two locations along the spicule marked in Fig. 1b. The two light curves are average intensities obtained from the same colored regions as are shown in Fig. 1b. Panel b: space-time map from slit a–b along the spicule shown in Fig. 1b. The slanted dotted lines are for reference to indicate the propagating speeds. See Sect. 2.2 and Appendix B.2 for details.