Earth's core variability from the magnetic and gravity field observations

Abstract

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 to 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.

Uncertainty of Low‐Degree Space Gravimetry Observations: Surface Processes Versus Earth's Core Signal

“…Recently, Saraswati et al. (2023) applied Singular Value Decomposition, Principal Component Analysis, and Multivariate Singular Spectrum Analysis to separate distinct spatio‐temporal patterns in magnetic and gravity field. Moreover, synthetic tests based on modeled processes have to be performed to evaluate the sensitivity of these methods with respect to Earth's core signals.…”

“…In order to detect tiny signals related to the core more sophisticated methods are needed such as empirical orthogonal function analysis (Schmeer et al, 2012) or independent component analysis (Frappart et al, 2011). Recently, Saraswati et al (2023) applied Singular Value Decomposition, Principal Component Analysis, and Multivariate Singular Spectrum Analysis to separate distinct spatio-temporal patterns in magnetic and gravity field. Moreover, synthetic tests based on modeled processes have to be performed to evaluate the sensitivity of these methods with respect to Earth's core signals.…”