AI 中文总结
该研究发现地球自转存在约70年的地核相关调制，通过分析1883-2022年数据明确其周期、振幅及与地核角动量的关联，指出该分量本身不直接要求引入负闰秒，为地球自转变率提供了地核贡献的证据。
AI 中文摘要
近日对世界时（UT1）的观测显示地球自转正在加速。若按现行闰秒框架持续下去，这种情况最终可能会促使考虑引入负闰秒。我们研究近期的自转加速是否与日长（LOD）的约70年地核相关调制一致。在扣除已建模的潮汐、地表流体及长期项贡献后，剩余日长包含一个近70年的分量，且从地磁观测推断得到的地核角动量（CAM）等效日长中也存在类似分量。本文所有谐波、频谱及日长-地核角动量分析均采用1883年至2022年的共同时间区间。对50至100年的试验周期进行谐波回归，得到剩余日长的周期为69.7年，地核角动量等效日长的周期为71.8年，振幅分别为2.87毫秒和1.94毫秒。Lomb-Scargle频谱在67.8年和70.5年附近显示峰值。这两个年序列的零滞后相关系数为0.918；其滞后相关在CAM超前约1至3年时出现宽峰值，其中在超前2年时数值达到最大值0.932。由于两个序列均具有强自相关性，这些系数用于表征它们的对应关系，而非评估预测意义。结果表明地核对低频自转变率有贡献，但无法唯一区分电磁、地形、引力及粘性核幔耦合机制的贡献。在拟合模型范围内，仅多年代际分量并不表明日长会在近期持续缩短，而这本身需要负闰秒。这是一项依赖模型的地球物理评估，并非对未来协调世界时（UTC）调整的业务预测。
英文摘要
Recent observations of Universal Time (UT1) indicate an acceleration in Earth's rotation. If sustained under the current leap-second framework, this behavior could eventually prompt consideration of a negative leap second. We examine whether the recent acceleration is consistent with an approximately 70-year, core-related modulation of length of day (LOD). After removal of modeled tidal, surface-fluid, and secular contributions, residual LOD contains a near-70-year component, and a similar component is present in core angular momentum (CAM)-derived equivalent LOD inferred from geomagnetic observations. All harmonic, spectral, and LOD-CAM analyses reported here use the common 1883--2022 interval. Harmonic regression over trial periods of 50--100 yr gives periods of 69.7 yr for residual LOD and 71.8 yr for CAM-derived equivalent LOD, with amplitudes of 2.87 and 1.94 ms, respectively. Lomb--Scargle spectra show peaks near 67.8 and 70.5 yr. The annual series have a zero-lag correlation of 0.918. Their lagged correlation has a broad maximum for a CAM lead of approximately 1-3 yr, with a numerical maximum of 0.932 at 2 yr. Because both records are strongly autocorrelated, these coefficients are used to characterize their correspondence rather than to assess predictive significance. The results are consistent with a core-related contribution to low-frequency rotational variability, but they do not uniquely separate the contributions of electromagnetic, topographic, gravitational, and viscous core--mantle coupling mechanisms. Within the fitted model, the multidecadal component alone does not indicate sustained near-term shortening of the day that would, by itself, require a negative leap second. This is a model-dependent geophysical assessment, not an operational prediction of future UTC adjustments.
Comments27 pages, 7 figures, Earth, Planets and Space accepted
