The top panel shows the distribution of the narrowband powers at Hα − 0.4 Å on slit 4. The bottom row (from left to right) shows the time–space diagram at Hα − 0.4 Å along slit 4, and its frequency-filtered components with P = 2.2–2.6 minutes and P = 4.2–5.7 minutes. The dotted lines mark the boundaries of LB 1.