New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

Abstract

AbstractThe intradecadal fluctuations in the length‐of‐day variation (∆LOD) are considered likely to play an important role in core motions. Two intradecadal oscillations, with ∼5.9 and ∼8.5 years periods (referred to as SYO and EYO, respectively), have been detected in previous studies. However, whether the SYO and the EYO have exhibited stable damping trends since 1962 and whether geomagnetic jerks are possible excitation sources for the SYO/EYO are still debated. In this study, based on different methods and different ∆LOD records with different time spans, we showed robust evidence to prove that the SYO and the EYO have had no stable damping trends since 1962. We also found that there may be a ∼7.6 years signal, but given that its average amplitude is too small, further confirmations are needed in the future. After confirming that the jerks have no special consistency with the peaks/valleys of the EYO/SYO, we further used a deconvolution process and confirmed that the geomagnetic jerks seem to be related to sudden changes in the SYO/EYO time series and their excitation series. Thus we finally suggest that jerks are possible excitation sources of the SYO/EYO. After using a deconvolution process, we estimate that the period P and quality factor Q of the SYO and the EYO are [P = 5.85 ± 0.06 years, Q ≥ 180] and [P = 8.45 ± 0.17 years, Q ≥ 350], respectively.