Swarm probes weakening of Earth’s magnetic field

Credit: NASA

This BBC link includes a video which shows the weakening of the magnetic field over the last 400 years (under ‘Magnetic flip’ sub-heading).
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In an area stretching from Africa to South America, Earth’s magnetic field is gradually weakening, says Phys.org.

This strange behaviour has geophysicists puzzled and is causing technical disturbances in satellites orbiting Earth.

Scientists are using data from ESA’s Swarm constellation to improve our understanding of this area known as the ‘South Atlantic Anomaly.’

Earth’s magnetic field is vital to life on our planet. It is a complex and dynamic force that protects us from cosmic radiation and charged particles from the Sun.

The magnetic field is largely generated by an ocean of superheated, swirling liquid iron that makes up the outer core around 3000 km beneath our feet. Acting as a spinning conductor in a bicycle dynamo, it creates electrical currents, which in turn, generate our continuously changing electromagnetic field.

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.

Earth’s magnetic field is often visualised as a powerful dipolar bar magnet at the centre of the planet, tilted at around 11° to the axis of rotation. However, the growth of the South Atlantic Anomaly indicates that the processes involved in generating the field are far more complex.

Simple dipolar models are unable to account for the recent development of the second minimum.

Continued here.