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Statistical Study of Magnetic Field Reversals in Geodynamo Models and Paleomagnetic Data

dc.contributor.advisorTilgner, Andreas Prof. Dr.
dc.contributor.authorMeduri, Domenico Giovanni
dc.titleStatistical Study of Magnetic Field Reversals in Geodynamo Models and Paleomagnetic Datade
dc.contributor.refereeChristensen, Ulrich Prof. Dr.
dc.subject.gokPhysik (PPN621336750)de
dc.description.abstractengThe most striking features in the temporal evolution of the Earth's dipolar magnetic field are polarity reversals and excursions. Several hundred polarity switches have been documented for the last two hundred million years of geomagnetic history and occur at irregular, apparently stochastic intervals. Self-consistent numerical dynamo models successfully reproduced several features of the geomagnetic field, including dipole field reversals. The causes for reversals and excursions, however, remain poorly understood. In this work, we aim to characterize the statistical properties of reversals and excursions in two geodynamo models and explore whether they reproduce paleomagnetic observations. These models undergo several hundred reversals, providing by far the longest numerical dynamo record to date. We investigated the statistics of reversal (and excursion) occurrences and durations using different distribution functions which describe diverse stochastic processes. The relative merit of each statistical model has been quantified using a Bayesian approach. In the numerical simulations analyzed here, the occurrence of reversals is best described by a homogeneous Poisson process. Similarly to paleomagnetic findings, the dipole moment has to decrease to about 30% of its mean to allow for reversals. The excursions during which the field intensity drops by a comparable margin have identical statistical properties to reversals and thus likely have the same internal origin. The simulations suggest that both type of events are simply triggered by large axial dipole fluctuations while other field components remain largely unaffected. The polarity epochs in our dynamo models show a statistic similar to the geomagnetic polarity intervals when simulating the limited time resolution of the paleomagnetic record. Our analysis suggests that deviations from a pure Poisson process in the geomagnetic reversal occurrences could be the consequence of the limited data quality rather than the signature of a different stochastic
dc.contributor.coRefereeWicht, Johannes Dr.
dc.subject.engfield reversalsde
dc.subject.engfield excursionsde
dc.subject.engnumerical simulationde
dc.subject.engBayesian statisticsde
dc.affiliation.instituteFakultät für Physikde

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