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South Atlantic Anomaly

  • 27 May 2020
  • 6 min read

Why in News

Recently, the Swarm constellation of satellites of the European Space Agency (ESA) has updated the development of South Atlantic Anomaly (SAA).

  • The South Atlantic Anomaly signifies weakening of the Earth’s magnetic field between Africa and South America.
    • However, it has been observed that the present dip in intensity of the Earth’s magnetic field is within the normal fluctuation levels.

Swarm Constellation Mission

  • Swarm is European Space Agency's first constellation of satellites for Earth observation.
  • It consists of three satellites designed to identify and precisely measure the different magnetic signals that make up Earth’s magnetic field.
  • The mission is operated by ESA's European Space Operations Centre (ESOC), in Germany, via the primary ground station in Kiruna, Sweden.

Earth’s Magnetic Field

  • Description:
    • Earth’s magnetic field, or the geomagnetic 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 Space including Sun.
    • The earth’s south magnetic pole is actually near the North Pole and the magnetic north pole is near the South Pole. This is why a compass magnet’s north pole actually points north (Since opposite poles attract each other).
  • Reasons for Presence:
    • The magnetic field of the Earth is due to the metallic and liquid outer core of the planet.
    • 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.
  • Significance:
    • It creates electric currents that generate and change our electromagnetic field.
    • The Northern Lights in the Polar Regions are 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.
    • The Earth's magnetic field also plays an important role in protecting the planet from solar winds and cosmic radiation that are harmful.

Key Points

  • Intensification of SAA (Weakening of Magnetic Field):
    • Scientists have discovered that Earth’s magnetic field has lost around 9% of its strength over the last 200 years.
    • Further, the strength of the field has dropped from around 24,000 nanoteslas to about 22,000 nanoteslas between 1970 and 2020.
    • It has also observed an intensified weakening of magnetic fields in the southwest of Africa. The eastern minimum of the South Atlantic Anomaly has appeared over the last decade and has been developing vigorously. This scenario indicates that the South Atlantic Anomaly could split into two separate low points.
  • Significance of SAA:
    • It has been speculated that the current weakening of the field is a sign of the pole reversal of the earth– in which the north and south magnetic poles may switch places.
      • Pole reversal is not an uncommon event and it takes place every 250,000 years. Last it had happened 7.8 lakh years ago.
    • Additionally, the SAA is expected to help to understand the processes in Earth’s core and future developments in the earth’s interior.
  • Implications:
    • At surface level, the South Atlantic Anomaly presents no cause for alarm. It means that people won’t feel the change even if the pole shift happens.
    • However, satellites and other spacecraft flying through the area are more likely to experience technical malfunctions. The weaker magnetic field in this region may force charged particles to penetrate the altitudes of low-Earth orbit satellites.
    • It may also affect the navigation-mapping, telecommunication and satellite systems which rely on the geomagnetic field. Therefore, computers, mobile phones and other devices could also face difficulties.

Way Forward

  • 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.
  • The magnetic field observations from the Swarm satellite are also expected to provide the new insights into the scarcely understood processes of Earth’s interior.


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