卫星观测揭示更短周期的内核振荡
Satellite observations reveal shorter periodic inner core oscillation
AI总结：
研究利用卫星大地测量数据从引力场Stokes系数中探测到约6年的内核振荡，其与地球日长变化信号相位相关，受控于内核与下地幔LLVPs的引力耦合，独立证实了内核存在比先前更短周期的振荡。
摘要：
由于无法直接接触，探测地球内核相对于地幔的运动是一项巨大的挑战。地震学观测最初为内核的差异性/超旋转提供了证据，但近期表明可能存在约70年的周期性振荡。这些对比鲜明的结果凸显了内核运动持续存在的谜团，使得相关争议悬而未决，包括精确的振荡周期。与地震观测并行，卫星大地测量积累了数十年的全球高精度记录，为探测内核运动提供了新途径。在此，我们从卫星观测导出的引力场2阶2次Stokes系数中探测到约6年的振荡，并发现它与地球日长变化中约6年信号具有独特的相位相关性。这种相关性归因于内核振荡，该振荡受控于内核与下地幔之间的引力耦合（主要由于两个大型低剪切速度省，LLVPs的密度非均匀性）。也就是说，我们独立证实了内核周期性振荡，尽管其周期比先前提出的要短得多。我们的研究结果证明了LLVPs的致密层（底部平均密度异常约为+0.9%），与潮汐层析成像和Stoneley模式的反演结果一致。此外，我们的研究揭示了内核边界约187 m的赤道地形起伏。
英文摘要：
Detecting the Earth's inner core motions relative to the mantle presents a considerable challenge due to their indirect accessibility. Seismological observations initially provided evidence for differential/super-rotation of the inner core, but recently demonstrated a possibly about 70-year periodic oscillation. The contrasting results underscore the ongoing enigma surrounding inner core motion, leaving debates unresolved, including the precise oscillate period. In parallel to seismic observations, satellite geodesy has accumulated decades of global high-precision records, providing a novel avenue to probe inner core motions. Here, we detect an about 6-year oscillation from the gravitational field degree-2 order-2 Stokes coefficients derived from satellite observations, and find it has a unique phase correlation with the about 6-year signal in the Earth's length-of-day variations. This correlation is attributed to an inner core oscillation which is controlled by the gravitational coupling between the inner core and lower mantle (mainly due to the density heterogeneity of the two large low-velocity provinces; LLVPs). That is, we independently corroborate the inner core periodic oscillation, albeit with a significantly shorter period than previously suggested. Our findings demonstrate the dense layer of the LLVPs (mean density anomalies of about +0.9 percent at the bottom), consistent with inversions from tidal tomography and Stoneley modes. Furthermore, our research reveals equatorial topographic undulations of about 187 m at the inner core boundary.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
