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Above South America, a weak spot in Earth’s magnetic field is evolving.
Called the South Atlantic Anomaly, this unique region has
been expanding for more than a decade.
And scientists believe that it’s beginning to split into two distinct zones.
Now, while this anomaly poses little risk to life here on Earth, it does allow scientists
to study the complicated mechanisms behind Earth’s magnetism.
Around 1800 miles below the surface, dynamic processes in Earth’s liquid iron outer core
are continuously generating electrical currents.
This account for the majority of Earth’s magnetic field.
But unlike a typical bar magnet, with one north and south pole, Earth’s magnetism
isn’t all neat and tidy.
If we take a look below the anomaly at the boundary separating the core and the mantle,
we can see the magnetic variations are much stronger.
This picture provides a clear link between the anomaly we see in Earth’s magnetosphere,
its origins deep within Earth’s interior, and
how it is projected to evolve in the near future.
This is important to understand, because our planet’s magnetic field plays a huge role
in shaping the near-Earth environment.
In addition to guiding compasses and animal migrations, the magnetic field acts like a
shield, repelling charged particles flung from the Sun that
could be disruptive if they reached the surface.
Many of the particles that do slip inside Earth’s protective bubble become trapped
in large rings of energetic particles called the Van Allen Belts, which are held in place
by Earth’s magnetic field.
The inner edge of the innermost belt is about 400 miles from the surface of Earth at the
equator, which keeps particle radiation a safe distance
from Earth and orbiting satellites.
But because of the offset between Earth’s magnetic and rotational poles, and the weakened
magnetic field over Southern Atlantic Anomaly, some energetic particles within the belts
penetrate closer to the Earth's surface.
This means that NASA and other space agencies need to account for the extra radiation when
low-orbit satellites pass through the anomaly.
Currently, NASA researchers are using data from satellites, along with theoretical models,
to track the evolution of the South Atlantic Anomaly, and help prepare for future challenges
to managing satellites and humans in space.
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