First panel: ratio between the maximum power (in the range 2−10 d) in the periodograms before correction and after correction (method 1) for various noise levels, showing the gain in power: no noise (solid line), 10 cm/s (dotted line), 20 cm/s (dashed line), 50 cm/s (dot-dashed line), 75 cm/s (dot-dot-dot-dashed line), 1 m/s (long-dashed line). The horizontal solid line represent a gain of A (i.e., no improvement). Second panel: same, but for the period range 10−40 d. Third panel: same, but for the period range 100−500 d. Fourth panel: same, but for the period range 500−800 d.