Total magnetic field Power Spectral Density (PSD) for August 30 2022 (upper) and September 05 2022 (lower) events. The left panels represent the 2-hour interval of PSD as a function of frequency upstream of the shock. The durations are labelled on the top right of the panel. 0 represents the time of shock. The thick solid line shows the power law of f^−5/3 for reference. The dashed vertical lines indicate the corresponding resonant frequencies of different energies by Taylor’s hypothesis. The three energies are labelled in the middle panel. The middle panels show the ratio of PSD as a function of time upstream of the shock, compared to the PSD closest to the shock (i.e., the PSD for the duration of [−2, 0] hours). The right panels show the fitted power law indices in the frequency range [0.003, 0.06] Hz as a function of time.