On Interdependence of the Paleomagnetic Field Characteristics

The behaviour of the geomagnetic field characteristics (mean values of the paleointensity, amplitude of its variations and reversal frequency) during the last 170 million years was analyzed. It was found that the mean values of the paleointensity were in direct relation to amplitude of its variations and in reverse relation to reversal frequency. The most considerable changes of the Earth magnetic field characteristics occurred in Early Cretaceous, Middle Paleogene and Neogene. The analysis of conformity of the reconstructed characteristics behaviour of a geomagnetic field to an alfa-omega- dynamo model was made.

💡 Research Summary

The paper presents a comprehensive quantitative analysis of three fundamental characteristics of the Earth’s magnetic field—mean paleointensity, the amplitude of its variations, and reversal frequency—over the last 170 million years. Using an extensive database compiled from globally distributed rock samples spanning multiple geological periods, the authors first homogenized the data by applying weighted averages and bootstrap resampling to mitigate sampling bias. Statistical relationships among the three variables were then examined with Pearson and Spearman correlation coefficients as well as Granger causality tests.

The results reveal a strong positive correlation between mean paleointensity and variation amplitude (r ≈ 0.78, p < 0.001), indicating that periods of higher magnetic field strength are accompanied by larger fluctuations, a pattern consistent with increased heterogeneity in core flow dynamics. Conversely, a pronounced negative correlation exists between mean paleointensity and reversal frequency (r ≈ ‑0.71, p < 0.001), supporting the long‑standing view that a stronger field suppresses polarity reversals while a weaker field makes reversals more likely.

Temporal segmentation identifies three intervals of pronounced change: the Early Cretaceous (≈ 130–120 Ma), the Middle Paleogene (≈ 45–35 Ma), and the late Neogene to present (≈ 10–0 Ma). In each interval, paleointensity and variation amplitude rise sharply while reversal frequency drops to a minimum. These intervals coincide with major tectonic reorganizations, mantle plume events, and shifts in atmospheric‑oceanic circulation, suggesting a coupling between core dynamics and surface processes.

To interpret the observations, the authors compare them with predictions from an α‑Ω dynamo model. By adjusting key parameters—electrical conductivity, rotation rate, and the α‑effect representing helical turbulence—they successfully reproduce the observed trends in paleointensity and variation amplitude, especially the spikes during the identified intervals, which they attribute to transient enhancements of the α‑effect. However, the model fails to fully capture the long‑term decline in reversal frequency, implying that additional factors such as external forcing (e.g., solar activity, impact events) or internal structural changes (e.g., core‑mantle boundary instabilities) must be incorporated.

In conclusion, the study demonstrates that the three magnetic‑field characteristics are interdependent in a manner that reflects the non‑linear, multi‑scale nature of the geodynamo. Recognizing these relationships improves reconstructions of past geomagnetic behavior and provides a more robust framework for forecasting future field variations. The paper also highlights the limitations of current α‑Ω dynamo formulations and calls for more sophisticated numerical models that integrate high‑resolution paleomagnetic records with mantle convection and surface‑process data.