Periodogram of the daily number of dust impacts with morphological types A and B recorded at L₁. The periodogram was evaluated at the DFT’s natural frequencies and oversampled by a factor of 15. The three most relevant frequencies and their harmonics are marked by vertical lines: the 365 d-period corresponding to the orbital period of the spacecraft (dotted green lines), the 6 d-period introduced by instrumental effects (dashed purple lines), and the solar rotation period at 27 d (solid brown lines). The bottom panel shows a zoomed-in view of the full spectrum with the estimated 95% significance thresholds indicated by a grey shaded area.