Over the past 200 years, Earth's magnetic field has lost around 9% of its strength. Meanwhile, a large region of reduced magnetic intensity has developed between Africa and South America — known as South Atlantic Anomaly. Over the past 5 years, however, a second center of minimum intensity has emerged southwest of Africa, suggesting that the South Atlantic Anomaly could split up into two separate cells.
Earth's magnetic field is vital to life on our planet– it is a complex and dynamic force that protects living beings from cosmic radiation and charged particles from the Sun.
The current prevailing understanding is that it's largely generated by a sea of superheated, swirling liquid iron that makes up Earth’s outer core around 3 000 km (1 864 miles) below the surface. It acts as a spinning conductor, producing electrical currents that generate the continuously changing electromagnetic field.
It's known that the field varies in strength and direction. For instance, recent studies have shown that the north magnetic pole's position is rapidly migrating toward Siberia.
For the past 200 years, the magnetic field has lost about 9 percent of its strength on a worldwide average.
Meanwhile, a large region of reduced magnetic intensity has developed between Africa and South America — known as the South Atlantic Anomaly.
The South Atlantic Anomaly refers to an area where our protective shield is weak. This animation shows the magnetic field strength at Earth’s surface from 2014-2020 based on data collected by the Swarm satellite constellation. Credit: ESA
The minimum field strength in this area has pummeled from 24 000 nanoteslas to 22 000 from 1970 to 2020. At the same time, the area of the anomaly has expanded and advanced westward at a pace of around 20 km (12 miles) per year.
In addition, for the past five years, a second center of minimum intensify has appeared southwest of Africa, indicating that the South Atlantic Anomaly could rupture into two separate cells.
The magnetic field is commonly pictured as a powerful dipolar bar magnet at the planet's core, tilted at about 11° to the axis of rotation. However, the growth of the anomaly signifies that the process involved in generating the field is more complex as simple dipolar models were not capable of accounting for the latest development of the second minimum.
The South Atlantic Anomaly refers to an area where our protective shield is weak. White dots on the map indicate individual events when Swarm instruments registered the impact of radiation from April 2014 to August 2019. The background is the magnetic field strength at the satellite altitude of 450 km (280 miles). Credit: ESA
Scientists from the Swarm Data, Innovation, and Science Cluster (DISC) used information from ESA's Swarm satellite constellation to study the anomaly and have a better understanding of it. Swarm satellites are built to determine and accurately measure the different magnetic signals comprising the Earth's magnetic field.
"The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously," said Jurgen Matzka from the German Research Center for Geosciences.
"We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth’s core driving these changes."
Image credit: ESA/ATG Medialab
Scientists have been speculating whether the present weakening of the field is an indication that the planet is heading for an imminent pole reversal, in which the north and south magnetic poles reverse places.
Such events have happened many times throughout the Earth's history, and we are long overdue by the average rate — roughly every 250 000 years at which the switch occurs.
While the mysterious origin of South Atlantic Anomaly is yet to be identified, ESA said that at the surface level it does not present a cause for alarm. However, satellites and other spacecraft flying through the area are more likely to experience technical malfunctions as the magnetic field is weaker in this region, so charged particles can penetrate the altitudes of low-Earth orbit satellites. In addition, SWARM scientists think the intensity dip in the South Atlantic occurring now is well within what is considered normal levels of fluctuations.
Featured image credit: ESA/ATG Medialab
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