Global Geological And Climatic Events

What is South Atlantic Anomaly?


From UPSC perspective, the following things are important :

Prelims level: Van Allen Radiation Belt, South Atlantic Anomaly

Mains level: South Atlantic Anomaly and its impact

New data obtained by the European Space Agency (ESA) Swarm satellites has revealed the existence of a mysterious anomaly weakening the Earth’s magnetic field. Termed as ‘South Atlantic Anomaly’, it extends all the way from South America to southwest Africa.

The term ‘South Atlantic Anomaly’ at its first sight looks similar to any climate/oceanic current related phenomena. But it’s not! This is where you can end up losing 2.66 marks in the prelims!

What is South Atlantic Anomaly (SAA)?

  • The SAA is referred to the behaviour of Earth’s Geo-Magnetic field in an area between Africa and South America.
  • The SAA is an area where the Earth’s inner Van Allen radiation belt comes closest to the Earth’s surface, dipping down to an altitude of 200 kilometres.
  • This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.
  • The effect is caused by the non-concentricity of the Earth and its magnetic dipole.
  • The SAA is the near-Earth region where the Earth’s magnetic field is weakest relative to an idealized Earth-centered dipole field.

Weakening of the magnetic field

  • Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average.
  • A large and rapid shrink has been observed in the SAA region over the past 50 years just as the area itself has grown and moved westward.
  • The weakening of the magnetic field is also causing technical difficulties for the satellites and spacecraft orbiting the planet.
  • The study conducted between 1970 and 2020, said that the magnetic field weakened considerably in a large region stretching from Africa to South America, known as the ‘SAA’.
  • This area has grown and moved westward at a rate of around 20 km per year.

Its impact

  • The magnetic shield has an important role to play in keeping unwanted radiation away as well as helping determine the location of magnetic poles.
  • Even though unlike global warming or any weather change, this anomaly doesn’t directly impact human lives, it could actually bring on a change in the way we access technology.
  • The reversal and apparent shift, which could keep extending could actually impact satellite and telecommunication system, which means that some of the internet and mobile phone functioning which depend on satellite signals can possibly get disrupted.
  • It could also affect the mapping and navigation systems in smartphones.
  • The weakening of earth’s magnetic field could also impact migratory movement.
  • Birds, animals- all those who migrate with the change in season depend on the earth’s mapping to move about can find it a little difficult.
  • This is only a possibility, but we don’t know the extent of the damage till now.

About the Van Allen Radiation Belt

  • A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet’s magnetic field.
  • The belts are located in the inner region of Earth’s magnetosphere. The belts trap energetic electrons and protons.
  • Earth has two such belts and sometimes others may be temporarily created.
  • Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays.
  • By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

Also read:

Shifting north magnetic pole forces urgent navigation fix

Back2Basics: Swarm  Constellation

  • Swarm is a European Space Agency (ESA) mission to study the Earth’s magnetic field.
  • It is ESA’s first constellation of satellites for Earth observation.
  • The Swarm constellation consists of three satellites (Alpha, Bravo and Charlie) placed in two different polar orbits, two flying side by side at an altitude of 450 km and a third at an altitude of 530 km.

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