Clock-like modulation of NB emissions. Panel a: clock or rotating beam test for 5 kHz NB. The horizontal axis of ω₀ encompasses the assumed modulation rates of 785 to 830° per day, which was chosen to be near the rotation rate of Saturn (10.7 hours = 807° per day). The vertical axis is the fitted peak-to-peak modulation power giving the fitted peak power of the 240-day time series under the assumption of each ω₀. The two solid lines show the modulation rates of 5 kHz NB emissions under the assumption of a clock-like source (red) and a rotating beam source (blue). Panel b: similar format as panel a but for 20 kHz NB emissions. The black dashed lines mark the modulation rate in the same 240-day window derived from the SKR intensities. The 5 kHz and 20 kHz NB time series used in this window are not separated into two hemispheres according to latitude.