Abstract In this paper, Singular Spectral Analysis (SSA) is applied to the geomagnetic field to delineate signatures from different sources, such as geomagnetic variability and lithospheric processes. We performed SSA on the Y component of the Swarm satellite magnetic field By during the period from September 2023 to January 2024. Eigen values obtained through SSA were correlated with geomagnetic indices Ap and Dst. λ1 decreases during disturbed geomagnetic conditions (Ap > 20, Dst −20 nT). The third eigenvalue (λ3) does not show a statistically significant correlation with the geomagnetic external source time series ( r = −0.005, p > 0.05), and is therefore used as a proxy for lithospheric processes. An earthquake of M7.6 occurred near the northern coast of Noto Peninsula on the west coast of Honshu, Japan on 1 January 2024. The temporal variation of the third eigenvalue λ3 from 120 days before the earthquake up to 30 days after it, shows a clear increase after the occurrence of Japan earthquake. A simultaneous anomaly of 0.5 nT in the first derivative of the Y component, 6 days before the earthquake supports the observed change in λ3. These anomalous changes in λ3 after the Japan earthquake support the correlation between anomalies extracted and the occurrence of earthquake aftershocks. Our analysis demonstrates that the SSA may be considered a promising tool for the extraction of anomalies associated with crustal activity.
Yadav et al. (Sun,) studied this question.