Wavelet analysis of the Hα line-center velocity fluctuations at the seven selected locations shown in Fig. 5. Left: results at the reference locations along the IRIS slit. Middle and right: corresponding wavelet power spectra at positions approximately 0.84 Mm below and 0.84 Mm above the reference locations, respectively. Top subpanel (in each panel): normalized velocity time series. The color map represents the wavelet power as a function of time and period, with the dotted red contours indicating the 99% confidence level. The cross-hatched regions mark the cone of influence. Rightmost subpanels: corresponding global wavelet power spectra, with the dotted red line indicating the 99% significance level. The gray-shaded region represents the period range between 2 and 4 minutes.