Top: mean power density in the 1000–1500 μHz region of the considered 30-day GOLF and Solar-SONG PSDs. Middle: mean power density ratio computed as the ratio between the mean power in the 2000–3500 μHz p-mode region and the 1000–1500 μHz region. Bottom: mean power density ratio computed as the ratio between the mean power in the 1700–2200 μHz region and the 1000–1500 μHz region. The dotted yellow line represents the value obtained with Solar-SONG during the 2018 campaign (represented by the yellow dot).