High above Earth, at an altitude of around 480km (300 miles), roughly over Brazil, there is a strange phenomenon. A place where satellites malfunction, the Hubble Space Telescope fails to gather data, and even astronauts aboard the International Space Station (ISS) are unable to conduct spacewalks.
This anomaly, which cannot be seen but is certainly present, is known as the South Atlantic Anomaly (SAA). It is often referred to as the Bermuda Triangle of Space.
What Causes the Anomaly?
The odd behavior of electronics in this region is due to a dip or dent in Earth’s magnetic field. While the magnetic field protects us from radiation in the form of charged particles, this region’s magnetic field is significantly weaker. This allows more dangerous particles to enter the area.
Dr. Ashley Greeley, a NASA heliophysicist, explains: “In this region, charged particles routinely travel closer to the surface of Earth than they do elsewhere.” These particles get trapped in the weak point of the magnetic field and can stay there for years, wreaking havoc on spacecraft.
“When energetic protons strike sensitive electronics, they can cause temporary issues like data loss or bit flips, or permanent damage where the electronics stop working completely,” she adds. “Charged particles can also accumulate on spacecraft surfaces, causing spacecraft charging, which damages electronic components.”
Space agencies and private companies take precautions, ensuring their satellites are turned off when passing through the SAA, and spacewalks are avoided in the area.
The Science Behind the Anomaly
The SAA is located within the Van Allen belts, two radiation belts surrounding the Earth. These belts trap energetic particles at high speeds, sometimes for thousands of years. However, the SAA is an area where the magnetic field is weaker, causing the particles to come much closer to the Earth’s surface, even within the range of low Earth orbit, where many satellites and the ISS orbit.
Despite being a concern for space missions, the SAA plays a vital role in protecting Earth’s space environment. Without the anomaly, there would be harsher radiation near the Earth’s atmosphere.
Prof. Yuri Shprits from the German Research Centre for Geosciences explains, “The SAA acts like a sink, drawing in energetic particles and keeping the rest of the orbit clear.”
The Mystery of Earth’s Core
The reason behind the South Atlantic Anomaly lies deep within Earth’s core, where temperatures reach thousands of degrees. The outer core, composed of liquid iron and nickel, creates the planet’s magnetic field. As this liquid metal moves due to convection, it creates a turbulent motion that generates the Earth’s magnetic field.
Dr. Monika Korte, a geomagnetism researcher, explains, “Hot material rises and cooler material sinks, and this convection becomes more turbulent, mixing up due to the Earth’s rotation.”
These turbulent motions create a dynamo effect, generating a massive magnetic field. However, this magnetic field is not perfectly uniform. Underneath the SAA, some regions have patches of reversed magnetic flux, which contributes to the anomaly.