Understanding rapid changes in Earth’s magnetic field: timing, spatial extent, and causes of geomagnetic spikes and excursions

Project Rationale
Earth’s constantly changing magnetic field is generated by the geodynamic motion of electrically conductive fluid in Earth’s outer core. Rapid and extreme changes of the field not only compromise Earth’s magnetic shielding protection from harmful cosmic rays and solar wind but also pose serious threat to the navigation technology and electrical infrastructure that underpin modern society. Alarmingly, palaeomagnetic records covering the last few tens of thousand years reveal that geomagnetic field has experienced rapid excursions and spike events during which its intensity either drops to only a few percent of the present level [1] or show extreme values greater than any observed in present and historical field [2]. These extreme changes place crucial constraints on the dynamics of the geodynamo. Yet, the lack of well dated high-resolution and continuous records from key locations has prevented us from answering many basic questions. For example, do geomagnetic spikes/excursions grow/decay in situ or move spatially through time? This project aims to make a step change in our understanding of extreme and rapid changes of the field by reconstructing continuous records of geomagnetic excursion and spike events at unprecedented resolution using multiple types of geological archives from a longitudinal transect around the globe.

Methodology
You will study marine and lake sediment sequences from the North Atlantic, UK, the Black Sea, and Japan, as well as cave deposits (stalagmites) from the UK and Japan. Magnetic properties of these materials will be analysed to help further select samples favourable for reconstructing reliable palaeomagnetic records. You will take advantage of a new type of instrument, Scanning SQUID Microscope (SSM), capable of analysing magnetic signal at ~100-micron resolution. Continuous and parallel precisely cut discrete sediment and stalagmite samples will be analysed on SSM in Japan and on a latest model of superconducting rock magnetometer at Southampton. Be isotopes will be analysed on selected samples to provide independent verification of geomagnetic intensity estimates. High-resolution oxygen isotope records, x-ray fluorescence (XRF) scan, together with any existing age constraints will be combined to create accurate chronology and detailed correlation for the study materials. In addition, selected archaeological artefacts from the UK and Japan and volcanic rock samples from Mountain Fuji will be studied to further verify and document the spatial extent of geomagnetic spike events in the UK and Japan.

Training
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in the School of Ocean and Earth Science. Specific training will include:
● Sampling and core analysis at repositories in Europe and/or Japan and work in the laboratories of Japanese collaborators
● High-precision age dating of marine and lake sediments
● Chemical analysis and imaging of sediment cores
● Palaeomagnetic and environmental magnetic analysis of sedimentary archives
● Managing and processing research data using quantitative analysis techniques including reconstructing reliable high-resolution palaeomagnetic records [3]
● Correlation, integration, and interpretation of multiple datasets for geomagnetic and environmental reconstructions
● Participation of international scientific meetings to present project results