Modiri Sadegh, Heinkelmann Robert, Belda Santiago, Malkin Zinovy, Hoseini Mostafa, Korte Monika, Ferrándiz José M, Schuh Harald
Department Geodesy, Federal Agency for Cartography and Geodesy (BKG), 60322 Frankfurt am Main, Germany.
GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany.
Sensors (Basel). 2021 Nov 13;21(22):7555. doi: 10.3390/s21227555.
The understanding of forced temporal variations in celestial pole motion (CPM) could bring us significantly closer to meeting the accuracy goals pursued by the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), i.e., 1 mm accuracy and 0.1 mm/year stability on global scales in terms of the Earth orientation parameters. Besides astronomical forcing, CPM excitation depends on the processes in the fluid core and the core-mantle boundary. The same processes are responsible for the variations in the geomagnetic field (GMF). Several investigations were conducted during the last decade to find a possible interconnection of GMF changes with the length of day (LOD) variations. However, less attention was paid to the interdependence of the GMF changes and the CPM variations. This study uses the celestial pole offsets (CPO) time series obtained from very long baseline interferometry (VLBI) observations and data such as spherical harmonic coefficients, geomagnetic jerk, and magnetic field dipole moment from a state-of-the-art geomagnetic field model to explore the correlation between them. In this study, we use wavelet coherence analysis to compute the correspondence between the two non-stationary time series in the time-frequency domain. Our preliminary results reveal interesting common features in the CPM and GMF variations, which show the potential to improve the understanding of the GMF's contribution to the Earth's rotation. Special attention is given to the corresponding signal between FCN and GMF and potential time lags between geomagnetic jerks and rotational variations.
对天极运动（CPM）中强迫性时间变化的理解，能够使我们更接近国际大地测量协会（IAG）的全球大地测量观测系统（GGOS）所追求的精度目标，即在全球尺度上，就地球定向参数而言，达到1毫米的精度和0.1毫米/年的稳定性。除了天文强迫作用外，CPM激发还取决于液核和核幔边界中的过程。同样的过程也导致了地磁场（GMF）的变化。在过去十年中进行了多项研究，以寻找地磁场变化与日长（LOD）变化之间可能存在的联系。然而，人们对地磁场变化与CPM变化之间的相互依存关系关注较少。本研究使用从甚长基线干涉测量（VLBI）观测中获得的天极偏移（CPO）时间序列，以及来自最先进地磁场模型的诸如球谐系数、地磁急变和磁场偶极矩等数据，来探究它们之间的相关性。在本研究中，我们使用小波相干分析来计算这两个非平稳时间序列在时频域中的对应关系。我们的初步结果揭示了CPM和GMF变化中有趣的共同特征，这显示出改善对地磁场对地球自转贡献理解的潜力。特别关注了自由核章动（FCN）与地磁场之间的对应信号，以及地磁急变与自转变化之间可能存在的时间滞后。
