Statistical study of magnetic field reversals in geodynamo models and paleomagnetic data

Auteurs

• Domenico Giovanni Meduri

Paramètres

• Manuels
• Manuels universitaires

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The Earth's dipolar magnetic field is characterized by polarity reversals and excursions, with several hundred documented switches over the last two hundred million years occurring at irregular intervals. While self-consistent numerical dynamo models have successfully reproduced features of the geomagnetic field, the underlying causes of these reversals and excursions remain unclear. This work aims to characterize the statistical properties of these events in two geodynamo models, which undergo several hundred reversals, yielding the longest numerical dynamo record to date. We analyzed the statistics of reversal and excursion occurrences and durations using various distribution functions representing different stochastic processes, assessing each model's merit through a Bayesian approach. Our findings indicate that the occurrence of reversals aligns best with a homogeneous Poisson process. Similar to paleomagnetic observations, the dipole moment must decrease to about 30% of its mean for reversals to occur. Excursions, which also see a comparable drop in field intensity, exhibit identical statistical properties, suggesting a common internal origin. The simulations imply that both events are triggered by significant axial dipole fluctuations, while other field components remain largely unaffected. Additionally, the polarity epochs in our models exhibit statistics akin to geomagnetic polarity intervals, indicating that deviation

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• Année de publication: 2015