NSFGEO-NERC: Deciphering the Dynamics of Geomagnetic Excursions
Lead Research Organisation:
University of Leeds
Department Name: School of Earth and Environment
Abstract
The most striking variations of Earth's magnetic field are polarity excursions and reversals. These events, in which the global field strength can significantly weaken, are central to understanding the processes that generate and sustain the geomagnetic field in the liquid core and the societal impacts that could arise from reduced magnetic shielding of the surface environment. Excursions have received relatively little attention compared to reversals despite occurring more frequently and lasting long enough to cause potentially significant societal disruption. Now new observational models spanning the past 100 kyr are illuminating the evolution of excursional fields in previously inaccessible detail, and combined with advances in numerical simulation of the field generation process, this paves the way for a new approach to understand such enigmatic events.
Several global spatial and temporal representations of Earth's magnetic field cover 0-100 ka or subsections thereof, and document up to 5 geomagnetic excursions with qualitative similarities as well as distinct differences. Formal definition of excursional field perturbations, duration, local asynchroneity, etc., can be made via the Paleosecular Variation Index allowing comparisons with numerical geodynamo simulations. Expanding the time interval to 0-120 ka we will produce the first high-resolution models with quantified uncertainty for the Post-Blake excursion at ~95 ka and the Hilina Pali excursion at ~20 ka. In parallel, numerical simulations will build on current NERC-funded research at Leeds that is defining the requirements for "Earth-like" field behavior. The focus of this proposal is to improve understanding of the nature and origin of geomagnetic excursions using these two synergistic interlinked components.
We will
(1) Use new and existing global and time-dependent observational models of several excursions during the last 120 kyrs to characterize field behavior before, during, and after excursions;
(2) Analyse the excursion mechanism and predictability in new geodynamo simulations conducted with a dominant force balance that reflects expected behavior in Earth's liquid outer core;
(3) Develop formal criteria for defining excursions and reconcile paleofield behavior with current and emerging views on Earth-like numerical dynamo simulations.
A vital aspect of this proposal is exploiting existing synergy between the Scripps Institution of Oceanography (SIO) observational geomagnetic field modelling and paleosecular variation analysis and Leeds simulations of core dynamics. Observational models will contribute to new Earth-like standards for simulations, which will in turn be used to make high-resolution predictions of observable field variations that can be sought in the lower resolution observational data. We expect to enhance understanding of the dynamics of geomagnetic excursions, including their predictability and relation to polarity reversals.
Several global spatial and temporal representations of Earth's magnetic field cover 0-100 ka or subsections thereof, and document up to 5 geomagnetic excursions with qualitative similarities as well as distinct differences. Formal definition of excursional field perturbations, duration, local asynchroneity, etc., can be made via the Paleosecular Variation Index allowing comparisons with numerical geodynamo simulations. Expanding the time interval to 0-120 ka we will produce the first high-resolution models with quantified uncertainty for the Post-Blake excursion at ~95 ka and the Hilina Pali excursion at ~20 ka. In parallel, numerical simulations will build on current NERC-funded research at Leeds that is defining the requirements for "Earth-like" field behavior. The focus of this proposal is to improve understanding of the nature and origin of geomagnetic excursions using these two synergistic interlinked components.
We will
(1) Use new and existing global and time-dependent observational models of several excursions during the last 120 kyrs to characterize field behavior before, during, and after excursions;
(2) Analyse the excursion mechanism and predictability in new geodynamo simulations conducted with a dominant force balance that reflects expected behavior in Earth's liquid outer core;
(3) Develop formal criteria for defining excursions and reconcile paleofield behavior with current and emerging views on Earth-like numerical dynamo simulations.
A vital aspect of this proposal is exploiting existing synergy between the Scripps Institution of Oceanography (SIO) observational geomagnetic field modelling and paleosecular variation analysis and Leeds simulations of core dynamics. Observational models will contribute to new Earth-like standards for simulations, which will in turn be used to make high-resolution predictions of observable field variations that can be sought in the lower resolution observational data. We expect to enhance understanding of the dynamics of geomagnetic excursions, including their predictability and relation to polarity reversals.
People |
ORCID iD |
| Christopher Davies (Principal Investigator) |