Compass readings that do not show true north and interference with satellite operations are a few of the problems caused by the properties of Earth’s magnetic field.
The magnetic field radiates around the globe and far into space, but is defined by processes deep in Earth’s core, where temperatures exceed 5,000 degrees Celsius.
New research by geophysicists at the University of Leeds suggests that the manner in which this super-hot core is cooled is key to understanding the causes of the peculiar properties — or anomalies, as scientists call them — of Earth’s magnetic field.
Dynamo at the center of the Earth
In the scorching temperatures deep within the Earth, the core is a mass of molten iron that acts like a dynamo. As the molten iron moves, it generates the Earth’s global magnetic field.
Convective currents keep the dynamo spinning as heat flows from the core into the mantle, a rocky layer that extends 2,900 kilometers up to Earth’s crust.
Research by Dr Jonathan Maund and Professor Christopher Davies, from the School of Earth and the Environment at Leeds, found that this cooling process does not occur in a uniform way across the Earth – and these differences cause anomalies in the Earth’s magnetic field.
Variations in the Earth’s magnetic field
Seismic analysis determined that there are regions in the mantle, under Africa and the Pacific Ocean for example, that are particularly hot. Computer simulations conducted by the researchers revealed that these hot regions reduce the cooling effect on the core – and this causes regional or local changes in magnetic field properties.
For example, when the mantle is hotter, the magnetic field at the top of the core is likely to be weaker.
This results in a weaker magnetic field projected into space over the southern Atlantic Ocean, causing problems for orbiting satellites.
intervention in space technology
Dr Maund, who led the study, said: “One of the things the magnetic field in space does is deflect charged particles emitted from the sun. When the magnetic field is weaker, this protective shield is not very effective.
“So, when satellites pass over that region, these charged particles can disrupt and interfere with their operations.”
Scientists have known about the anomaly over the South Atlantic Ocean since they began observing and monitoring the magnetic field, but it is unknown if it is a long-lived feature or something that happened more recently in Earth’s history.
As the study in Leeds revealed, the anomalies are likely caused by differences in the rate of heat flow from the Earth’s core into the mantle. It is likely that these differences in the flow of heat, in the internal structure of the Earth, determine how long it can last.
Dr Maund added: “Processes in the mantle are happening very slowly, so we can expect the anomalies in temperature in the lower mantle to remain unchanged for tens of millions of years. years.
“But the hotter outer core is a quite dynamic fluid region. So the heat fluxes and the magnetic field properties that cause them will likely fluctuate on shorter time scales, perhaps 100 to 1,000 years.”
The paper – longitudinal structure of Earth’s magnetic field controlled by low mantle convection flow – is published in Nature Geoscience. When the ban is lifted, it can be downloaded from a file Natural Earth Sciences website. https://www.nature.com/articles/s41561-023-01148-9
