Earth’s magnetic field is gradually weakening in an area that stretches from Africa to South America, and scientists who are trying to understand why.
This weakening is also causing technical disturbances in some satellites orbiting Earth.
Scientists are using data from the European Space Agency’s Swarm constellation to improve our understanding of this area, which is known as the ‘South Atlantic Anomaly.’
Among other things, Earth’s magnetic field protects humanity from space radiation and super-charged particles emanating from the sun.
This field is far from static and varies both in strength and direction. For example, recent studies have shown that the position of the north magnetic pole is changing rapidly.
Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average. A large region of reduced magnetic intensity has developed between Africa and South America and is known as the South Atlantic Anomaly.
From 1970 to 2020, the minimum field strength in this area has dropped from around 24 000 nanoteslas to 22 000, while at the same time the area of the anomaly has grown and moved westward at a pace of around 20 km per year.
Over the past five years, a second centre of minimum intensity has emerged southwest of Africa — indicating that the South Atlantic Anomaly could split up into two separate cells.
According to the ESA, the magnetic field is generated by an extremely hot swirling liquid iron that comprises the planet’s outer core – which is about 3,000 kilometers under our feet.
“The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously,” said Jürgen Matzka in a statement.
“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.“
The South Atlantic Anomaly refers to an area where our protective shield is weak. In the video by Division of Geomagnetism, DTU Space below, the 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.
It has been speculated whether the current weakening of the field is a sign that Earth is heading for an imminent pole reversal — in which the north and south magnetic poles switch places.
Such events have occurred many times throughout the planet’s history and even though we are long overdue by the average rate at which these reversals take place (roughly every 250 000 years), the intensity dip in the South Atlantic occurring now is well within what is considered normal levels of fluctuations.