Why in the news?

  • Recent findings from the European Space Agency’s (ESA) Swarm mission reveal that the South Atlantic Anomaly (SAA) — the region of weakest intensity in Earth’s magnetic field — has expanded by nearly 0.9% since 2014.

South Atlantic Anomaly (SAA)

  • What is it?:
    • The South Atlantic Anomaly (SAA) is a region over the South Atlantic Ocean and parts of South America and Africa where Earth’s magnetic field is significantly weaker than elsewhere. 
    • This anomaly allows charged particles from the inner Van Allen radiation belt to come unusually close to Earth’s surface, increasing radiation exposure for satellites and spacecraft operating in low Earth orbit (LEO).
  • Extent: From the southern tip of South America to the mid-Atlantic Ridge, including parts of Brazil and Angola.
  • Causes for SAA:
    • The South Atlantic Anomaly (SAA) arises from irregular movements of molten iron and nickel within Earth’s outer core, which disturb the geo-dynamo- the process responsible for generating Earth’s magnetic field.
    • Beneath the South Atlantic, scientists have detected reverse flux patches- zones where magnetic field lines dive back into the Earth rather than emerging outward, thereby reducing local magnetic strength.
    • These intricate interactions between the core and mantle lead to spatial variations in magnetic intensity, resulting in the formation of the SAA.
    • Geomagnetic secular variation: The SAA is slowly shifting westward and growing in area as the geomagnetic field weakens over time.
  • Effects and Impacts of SAA:
    • Impact on Space Assets:
      • High radiation dose: Trapped protons cause elevated ionizing radiation, affecting satellites in LEO (including the International Space Station, Hubble Telescope, and communication satellites).​
      • Malfunctions and data corruption: Satellite computers may crash due to bombardment by charged particles. e.g., NASA reported Shuttle laptop crashes during traversals through SAA.​
      • Component degradation: Radiation increases wear on electronic systems and solar panels.
    • Impact on Astronauts:
      • Astronauts report seeing “phosphenes”- light flashes from cosmic rays hitting the retina when passing through SAA.
    • Scientific Implications:
      • Helps scientists study geomagnetic field evolution, core dynamics, and space weather effects.
      • Provides insights into possible geomagnetic reversals and long-term magnetic weakening.