Abstract. The motions of the liquid within the Earth's outer core lead to magnetic field variations together with mass distribution changes. As the core is not accessible for direct observation, our knowledge of the Earth’s liquid core dynamics only relies on indirect information sources. Mainly generated by the core dynamics, the surface geomagnetic field provides information about the variations of the fluid motion at the top of the core. The dynamic of the fluid core is also associated with mass distribution changes inside the core and produces gravitational field time fluctuations. By applying several statistical blind source separation methods to both the gravity and magnetic field time series, we investigate the common space–time variabilities. We report several robust interannual oscillations shared by the two observation sets. Among those, a common mode of around 7 years looks very significant. Whereas the nature of the driving mechanism of the coupled variability remains unclear, the spatial and temporal properties of the common signal are compatible with a core origin.

中文翻译：

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磁场和重力场观测的地核变化

摘要。地球外核内液体的运动导致磁场变化以及质量分布变化。由于地核无法直接观测，我们对地球液态地核动力学的了解仅依赖于间接信息来源。表面地磁场主要由核心动力学产生，提供有关核心顶部流体运动变化的信息。流体核心的动态还与核心内部的质量分布变化相关，并产生引力场时间波动。通过将几种统计盲源分离方法应用于重力和磁场时间序列，我们研究了常见的时空变化。我们报告了两个观测集共有的几个强劲的年际振荡。其中，7年左右的常见模式显得非常重要。尽管耦合变异性驱动机制的本质仍不清楚，但公共信号的空间和时间特性与核心起源兼容。