Wavelet analysis results for slits 2 and 9 (see Fig. 1) in 171 Å. Top two panels in each of these show the light curves, original and background-trend-subtracted, for the region enclosed by horizontal lines in Fig. 2. The bottom left panel shows the wavelet plot with contours enclosing the 99% confidence regions, for a white-noise process. Bottom right panel is the global wavelet plot with 99% global confidence level, overplotted as a dotted line. The periods of primary and secondary peaks are also written in the text (middle-right). Corresponding plots in 193 Å  are shown in Fig. 5.