Geomagnetic Field Variations in Numerical Dynamo Simulations Spanning Multi-Millennial Timescales

Stephen Mason (University of Leeds)

Wednesday 28th February 15:00-16:00 Maths 309

Abstract

Analyzing the characteristics of variations in the strength and direction of the geomagnetic field can inform us about physical processes within the Earth's core. Paleomagnetic studies have found rates of change in the field's intensity reaching around 1.5µT/yr at 1000 BCE, compared to maximum values of around 0.12 µT/yr in the present day, while changes in the direction over the past 100 kyrs can exceed those seen in the modern field by a factor of 10. Results from geodynamo simulations have recreated rapid changes in intensity and direction and attributed these events respectively to migration of normal and reversed flux patches across the core surface. However, matching the spectrum of geomagnetic variability that has been uncovered in recent models of the field over the last 10-100 kyrs has not been systematically explored in simulations. We will present results from a new suite of Earth-like dynamo simulations with the force balance and non-dimensional output parameters matching the expected regime of the geodynamo. We will analyze the rates of change of the intensity, direction, and activity of the simulated field, as well as more general extreme changes such as polarity excursions. These results will then be linked to paleomagnetic observations, using the latest data spanning the last 100000 years, enabling us to characterize the observed changes and relate them to the underlying mechanisms in the core.

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