Compass readings that do not show true north and interfere with the operation of satellites are just some of the problems caused by the characteristics of the Earth’s magnetic field. The magnetic field pervades the entire earth and space, but is determined by processes occurring deep in the Earth’s core, where the temperature exceeds 5000 degrees Celsius.
A new study by geophysicists at the University of Leeds shows that the way this superheated core cools is key to understanding the causes of features – or anomalies as scientists call it – in Earth’s magnetic field.
dynamo at the center of the earth
At the extremely high temperatures observed in the depths of the Earth, the core is a rotating mass of molten iron that acts like a dynamo. As the molten iron moves, it creates the Earth’s global magnetic field. Convective currents spin the dynamo as heat flows from the core to the mantle, a layer of rock that extends 2,900 kilometers into the earth’s crust.
Research by Dr Jonathan Maund and Professor Christopher Davies from the School of Earth and Environment in Leeds found that this cooling process does not occur evenly across the Earth, and that these fluctuations cause anomalies in the Earth’s magnetic field.
Changes in the Earth’s magnetic field
Seismic analyzes revealed that there are particularly warm regions of the mantle, such as Africa and the Pacific Ocean. Computer simulations conducted by the researchers showed that these hot regions reduce the cooling effect of the core, resulting in regional or local changes in the properties of the magnetic field.
For example, where the mantle is warmer, the magnetic field at the top of the core will likely be weaker. This results in a weaker magnetic field being projected into space over the South Atlantic, creating problems for orbiting satellites.
Intervention in space technology
“One of the things the magnetic field does in space is deflect charged particles emitted by the sun,” said Dr Maund, who led the study. When the magnetic field is weaker, this protective shield is not as effective.
“So when satellites fly over that region, these charged particles can disrupt their operation.”
Scientists have known about the anomaly over the South Atlantic since they began monitoring and observing the magnetic field, but it is unknown whether it is a longstanding feature or something that occurred very recently in Earth’s history.
According to the Leeds study, the anomalies are likely due to a difference in the rate at which heat flows from the Earth’s core to the mantle. Where they reside in the interior of the world likely determines how long they will last.
Dr Maund added: “Mantle processes are very slow, so we can expect temperature anomalies in the lower mantle to remain constant over tens of millions of years. So we expect the properties of the magnetic field they create to remain unchanged. They will also be similar over tens of millions of years.
“But the warmer outer core is a highly dynamic fluid region. So the heat fluxes and the magnetic field properties they cause are likely to oscillate on shorter time scales, perhaps 100 to 1,000 years.”
Source: Port Altele