NSFGEO-NERC: CSEDI-On the origin of extreme variations in Earth's magnetic field

点击翻译按钮获取中文摘要

This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own ivestigators and component of the work.Earth’s internal magnetic field is generated deep in the planet’s liquid outer core and provides many benefits to its human inhabitants. It serves as a protective shield from the space weather generated by the solar wind, inhibits potentially damaging cosmic rays from reaching the surface, and has long served as a fundamental aid for navigation. Knowledge of its current structure is an intrinsic part of the digital mapping tools embedded in every smartphone, highlighting the importance of understanding what causes any unexpected changes. Extreme changes in both direction and strength of the magnetic field have occurred in the geological and archeological records, in the form of geomagnetic excursions, polarity reversals, and rapid intensity variations known as geomagnetic spikes. These will be studied under this project. An integral aspect of the work will be building synergistic approaches across communities interested in the geological record of the magnetic field and realistic computational simulations of its behavior. Understanding the physical origins of these changes will enhance our basic understanding of Earth’s magnetic field, and enable collaborations with related geophysical communities interested in Earth’s deep interior and other planets. New methodologies will be developed to study extreme changes in the geomagnetic field and this project will enable education, training and research mentoring for undergraduate, graduate, and postdoctoral researchers, while developing further international collaborations with NERC sponsored investigators at Leeds University, UK. This work will improve understanding of what drives extreme events using two synergistic components. A multi-scale modeling approach based on spherical triangle tessellations (STT) on the surface of Earth’s core will improve regional resolution in global magnetic field models. A new suite of geodynamo models will access the rapidly rotating regime appropriate to Earth’s liquid core. The results will be combined to assess potential physical interpretations of empirical signatures of extreme events. Extreme field variations present a challenge to standard regularized spherical harmonic representations which rely on trade-offs between data misfit and global measures of spatial and temporal complexity. The STT representation will allow finer spatial and temporal resolution in regions of high data density and lower resolution with limited data, enabling robust imaging of extreme regional field behavior. A new regime diagram describing the behavior of non-magnetic convection with Earth-like geometry, buoyancy forcing, and heat flow heterogeneity at the outer boundary illuminates the parameter combinations needed for simulations to realize the rapidly rotating and turbulent dynamics that are thought to arise in the liquid core. Recent advances in dynamo theory will be used to devise simulations that produce strong magnetic forces as likely occur in the core, following a distinct path towards Earth-like rotation rates and diffusivities while remaining in the rapidly rotating regime. Both new and existing tools will be used to assess the morphological and temporal similarity between these simulations and new geomagnetic field models, characterize extreme changes in intensity and direction of the observable field, and relate these to the underlying magnetohydrodynamic processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.