Panel (a) distribution of the narrowband oscillation powers along slit 1 as shown in Figure 1(a). Time–space diagrams for slit 1 are shown in panels (b)–(f). (b) Doppler velocity, (c): Hα − 0.4 Å, and (d)–(f) the filtered components of the Hα − 0.4 Å diagram in the frequency ranges of 2.2–2.6 minutes, 2.7–4.1 minutes and 4.2–5.7 minutes, respectively. White dotted lines mark the umbral boundaries.