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Above South America, a weak spot in Earth’s
magnetic field is evolving.

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Called the South Atlantic Anomaly, this unique
region has

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been expanding for more than a decade.

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And scientists believe that it’s beginning
to split into two distinct zones.

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Now, while this anomaly poses little risk
to life here on Earth, it does allow scientists

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to study the complicated mechanisms behind
Earth’s magnetism.

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Around 1800 miles below the surface, dynamic
processes in Earth’s liquid iron outer core

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are continuously generating electrical currents.

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This account for the majority of Earth’s
magnetic field.

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But unlike a typical bar magnet, with one
north and south pole, Earth’s magnetism

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isn’t all neat and tidy.

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If we take a look below the anomaly at the
boundary separating the core and the mantle,

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we can see the magnetic variations are much
stronger.

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This picture provides a clear link between
the anomaly we see in Earth’s magnetosphere,

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its origins deep within Earth’s interior,
and

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how it is projected to evolve in the near future.

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This is important to understand, because our
planet’s magnetic field plays a huge role

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in shaping the near-Earth environment.

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In addition to guiding compasses and animal
migrations, the magnetic field acts like a

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shield, repelling charged particles flung
from the Sun that

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could be disruptive if they reached the surface.

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Many of the particles that do slip inside
Earth’s protective bubble become trapped

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in large rings of energetic particles called
the Van Allen Belts, which are held in place

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by Earth’s magnetic field.

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The inner edge of the innermost belt is about
400 miles from the surface of Earth at the

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equator, which keeps particle radiation a
safe distance

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from Earth and orbiting satellites.

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But because of the offset between Earth’s
magnetic and rotational poles, and the weakened

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magnetic field over Southern Atlantic Anomaly,
some energetic particles within the belts

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penetrate closer to the Earth's surface.

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This means that NASA and other space agencies
need to account for the extra radiation when

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low-orbit satellites pass through the anomaly.

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Currently, NASA researchers are using data
from satellites, along with theoretical models,

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to track the evolution of the South Atlantic
Anomaly, and help prepare for future challenges

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to managing satellites and humans in space.

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