Rapid Variations of Earth’s Magnetic Field

Schematic illustration of the magnetic field lines generated by the Earth. Image credit: Peter Reid, University of Edinburgh

Earth’s magnetic field provides a barrier shielding Earth from harmful cosmic rays as well as helping sustain our atmosphere by deflecting the solar wind. It is produced by a geodynamo from the swirling motions of molten iron and nickel deep in Earth’s interior. These movements in the liquid core trigger the magnetic field to constantly change. A new study by Christopher Davies of the University of Leeds and Catherine Constable of the Scripps Institution of Oceanography at the University of California at San Diego suggests that Earth’s magnetic field can change ten times faster than previously thought. They used a numerical model of the geodynamo to simulate the flow of material in Earth’s liquid core and how it has influenced the movement of Earth’s magnetic field over the past 100,000 years. The results of the simulations show that Earth’s magnetic field can shift in direction at a rate of up to approximately 10° per year, which is almost ten times faster than found in previous paleomagnetic studies and one hundred times faster than currently observed. These rapid changes in magnetic field direction are associated with times when the field is unusually weak and generally occur during geomagnetic reversal. For example, during one extreme event of reversal of the Earth’s magnetic field, known as the Laschamp event, the magnetic field weakened to around five percent of what it is today. The simulation also suggested that rapid directional changes tend to take place at lower latitudes (<40°) where the magnetic field is weaker, which could be helpful in guiding future paleomagnetic fieldwork. The results of these simulations are in agreement with recent observational models and indicate that rapid changes in Earth’s magnetic field can be explained by the physics of the geodynamo. READ MORE