Catastrophic change in the Earth's magnetic field

Earth's magnetic field provides a protective shield from harmful effects of the solar wind, but field strength and behaviour are constantly changing. Even a modestly weakened magnetic field poses a serious threat to the satellite and aviation technology and electrical infrastructure that underpin modern society. Alarmingly, geological records spanning the last few hundred thousand years reveal spectacular geomagnetic excursion events during which the field intensity drops to only a few percent of the present level while field direction temporarily reverses for a few centuries or so. These excursions have been observed in magnetic records from volcanic lavas, marine/lake sediments, wind-blown dust accumulations and cave deposits, and in chemical records from ice cores and sediments showing dramatically increased cosmic radiation. Yet we do not understand the cause or the consequences of these events. Data available for even the best-documented excursion (which occurred ~41 thousand years ago) is insufficient to answer basic questions such as: What happens to the structure of geomagnetic field during an excursion? Does it maintain a mainly dipolar structure (like a bar magnet) or does it become more complex? Do magnetic field excursions start and end synchronously around the globe?
Building upon existing collaborations between a team of UK and Japanese scientists, this project will combine novel and traditional methods to make a step change in the resolution of paleomagnetic records achievable from sediment archives to tackle fundamental questions on field behaviour. We will take advantage of a novel instrument (SQUID Microscope) and latest model of superconducting rock magnetometer to study a selected set of sediment archive from the Atlantic Ocean and Japanese lakes that contain geomagnetic excursions. The results will be used to build and exploit accurately dated/correlated continuous paleomagnetic records of excursion events at unprecedented (sub-millimetre) resolution, and provide new understanding of the structure and spatial variability of the Earth's magnetic field over the geomagnetic excursions.