The “dent” in Earth’s magnetic field

NASA is monitoring a strange anomaly in Earth’s magnetic field – a vast 
region of lower magnetic intensity in the skies above the South Atlantic

SOUTH ATLANTIC ANOMALY (SAA)

Expanding weak spot in Earth’s magnetic field which appears to be starting to split in two

Anomaly poses little risk to life on Earth, but same can’t be said
for spacecraft flying overhead

Magnetic field: Protects Earth from Sun’s charged particles

South America
Atlantic Ocean
Africa
Antarctica

——
Outer core: Spinning liquid iron (5,000°C), creates Earth’s magnetic field

African Large Low Shear Velocity Province: Huge reservoir of dense rock 2,900km below Africa. Disrupts generation of magnetic field 
– weakening it

VAN ALLEN BELTS
Geographical axis

Magnetic axis
N
axis

Crust
Inner Core
Mantle

Charged particles from Sun held in statis by Earth’s magnetic field
Inner belt: Charged particles can dip down where magnetic field is weaker, to around 200km from crust
 

Radiation threat: Low orbit satellites need to account for extra radiation
when passing through anomaly as it can cause electronics to short out. For safety, many satellites are routinely shut down before entering it


© GRAPHIC NEWS
Sources: ScienceAlert, National Geographic, Earth 3D
Diagrams not to scale