“…Ye et al (2022) used the time-frequency analysis CEEMDAN-CWT (Complete Ensemble Empirical Mode Decomposition with Adaptive Noise-Continuous Wavelet Transform) method to investigate 65 non-recurrent geomagnetic storms (Kp ≥ 7) that occurred during the 23rd and 24th solar activity cycle, and pointed out that geomagnetic storm precursor signals reconstructed from CRI by using this method could predict the occurrence of non-recurrent geomagnetic storms 22.5 hr in advance. Despite its effectiveness, the complexity of CRI limits its ability to remove the influence of ground level enhancement (GLE) events and predict moderate and small storms (Kp ≤ 6) (Ye et al, 2022). CRI exhibits a complex structure that includes both non-recurrent signals, such as GLE, FD, and CME-driven fluctuations (Belov & Gushchina, 2018;Dorman, 1999) and periodic signals, such as 22-year cycle, 11-year cycle, annual variation, seasonal variation, diurnal variation, and so on (Chowdhury et al, 2016;Jeong & Oh, 2022;Krymsky et al, 2005;Shen & Qin, 2017;Tezari et al, 2016).…”