Context

The Earth's magnetic field is weakening between Africa and South America, causing issues for satellites and space craft. Scientists studying the phenomenon observed that the South Atlantic Anomaly has grown considerably in recent years, though the reason for it is not entirely clear.

About

What is the magnetic field of Earth?

• Earth’s magnetic field is the magnetic field that extends from the Earth’s interior out into space exerting a force on the charged particles emanating from the Sun.
• It gets stretched out into a comet-like shape with a tail of magnetism that stretches millions of miles behind the Earth, opposite from the Sun. 
• The magnetic field of Earth protects the life of Earth from the harmful cosmic radiation and charged particles emitted from the Sun.

What causes it?

• The magnetic field of the Earth is due to the metallic and liquid outer core of the planet, around 3,000 km below our feet.
• It creates electric currents that generate and change our electromagnetic field. The outer core of the planet is like a giant dynamo.
• The rotation of the Earth creates movements inside the liquid outer core which gives rise to the geomagnetic field.
• The Northern Lights in the Polar Regions are also caused by the magnetic field of Earth – the energy particles emitted by the Sun are channelled by the Earth’s magnetic field towards the poles, where they interact with the atmosphere to create the aurora borealis.

What scientists have found?

• Using data gathered by the European Space Agency's (ESA) Swarm constellation of satellites, researchers noted that the area of the anomaly dropped in strength by more than 8 per cent between 1970 and 2020.
• The magnetic field has lost nearly nine per cent of its strength on a global average in the last 200 years.
• This year, the “minimum field strength” in the South Atlantic Anomaly has seen a drop of around 24,000 nanoteslas to 22,000 from its strength in 1970.
• The area of anomaly has also grown in this period. The patch has also moved fartherwest at a rate of roughly 12 miles per hour over the last 50 years.
• The last time a "geomagnetic reversal" took place was 780,000 years ago, with some scientists claiming that the next one is long overdue. Typically, such events take place every 250,000 years.

About South Atlantic Anomaly:

• The South Atlantic Anomaly (SAA) is a stretch between Africa and South America. 
• SAA is an occurrence that takes place due to something known as the Van Allen Radiation Belts.
• These Van Allen radiation belts are responsible for trapping radioactive particles near the coast of Brazil, which creates the SAA phenomenon.
  
  

Van Allen radiation belts:   A radiation belt refers to a layer of charged and energetic particles which is held by the planet’s magnetic field around the planet. The Van Allen belt specifically refers to the radiation belts around the Earth. The main constituents of the belts are believed to come from solar wind and cosmic rays. The belt is divided into two belts - outer and inner. The inner belt extends from roughly 600 miles to 3,700 miles, that is, from 1,000 km to 6,000 km above the earth's surface. The outer belt extends from 9,200 miles (15,000 km) to 15,600 miles (25,000 km) above the surface.

How will it impact?

• The weakening of magnetic field gives rise to speculations that Earth is heading for an eminent pole reversal, a phenomenon in which north and south poles switch places.
• The repercussions of such an event could be significant, as the Earth's magnetic field plays an important role in protecting the planet from solar winds and harmful cosmic radiation.
• Telecommunication and satellite systems also rely on it to operate, suggesting that computers and mobile phones could experience difficulties. The South Atlantic Anomaly is already causing issues with satellites orbiting Earth, while spacecrafts flying in the area could also experience "technical malfunctions".
• Birds, turtles and other creatures also use the magnetic field of Earth to navigate. In effect, the navigation systems and mapping functions in smartphones may be affected.

Conclusion:

The process is not an instantaneous one and could take tens of thousands of years to take place. The mystery of the origin of the South Atlantic Anomaly has yet to be solved. However, one thing is certain: magnetic field observations from Swarm are providing exciting new insights into the scarcely understood processes of Earth's interior.