(Top) Echelle diagram of the power spectrum for 29 years of LOI FD data. The double ridges close to the centre are the l = 0 − 2 modes, while the ridge on the right side are the l = 1 modes, sided by the faint ridge of the l = 3 modes. (bottom) Echelle diagram of the ratio of the power spectrum to that of the fitted model for 29 years. The remaining ridge on the left side are the l= 4 modes, with a faint ridge of the l = 7 modes going through. The remaining ridge at the center are the l= 5 modes.