Earth is an enormous magnet, of which its iron-rich core forms a shield Magnetic field that surrounds the planet —— well, almost. A “dent” in this magnetic field, known as the South Atlantic Anomaly, causes charged particles from the sun to dive closer to the planet in an area over South America and the South Atlantic Ocean.
These particles can at least be knives with instruments in space. That NASA scientists and other researchers have no choice but to adapt to this gate in the magnetic field, disable satellite instruments passing through the SAA and accept the loss of some data on instruments aboard the International Space Station ( ISS). They also keep close tabs on the SAA, according to a new article from NASA’s Goddard Space Flight Center.
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“Even though the SAA is moving slowly, it’s going through some change in morphology, so it’s also important that we observe it constantly,” said Terry Sabaka, a geophysicist at Goddard in Maryland, in the piece.
The anomaly
The Earth’s magnetic field is the product of its iron-rich outer core, which makes the field as it crawls around its inner core. The field protects the earth’s atmosphere from being slowly repelled by charged particles from the sun. It also protects electronic equipment on earth against the same bombardment.
Normally, particles are deflected from the sun by the field or trapped in two zones called the Van Allen belts, allowing the particles to move no closer than 644 kilometers (644 kilometers) from the earth’s surface. This offers a lot of space to protect the planet and its people launched by satellites. The ISS, for example, rotates about 350 miles (350 km) above the Earth’s surface.
But the magnetic field is weakened, which is why some scientists think so would be about to reverse, exchanges its north and south poles. (Alternatively, it may go through a weak phase and then strengthen again, as has happened in the past.) Reason for this weakening seems to be the South Atlantic Anomaly, a strange place of particular weakness that stretches between South America and Africa . The zone is changing, with recent research suggesting that it is evolving not one, but two, separate low points.
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Already, satellites passing through the SAA have to do so with many sensitive instruments turned off, according to Goddard. As the ISS passes through, some of the space station’s instruments are vulnerable to “blips” caused by the greater exposure to solar particles. The Global Ecosystem Dynamics Investigation (GEDI) mission, for example, experiences a power recovery about once a month and loses data every few hours thanks to the SAA.
Fortunately, “these events do not cause harm to GEDI,” said Bryan Blair, the mission’s deputy investigator and a scientist lidar instrument at Goddard, in the agency’s article.
The changes follow
Goddard scientists and their colleagues around the world are keeping tabs on the SAA, both to ensure that their operations are protected from the effects and to try to understand how the anomaly will change in the future.
Using data from SAMPEX (the Solar Anomalous and Magnetospheric Particle Explorer), a satellite launched in 1992 and collecting data until 2012, Goddard researchers learned that the SAA is moving slightly west, results published in the journal Space weather in 2016. The European Space Agency (ESA) launched a set of satellites known as Swarm in 2013 which provide detailed observations of the Earth’s magnetic field and changes in the SAA. It was data from Swarm satellites that showed the development of two separate points for minimum strength in the SAA, and hinted that the anomaly might split into two separate zones.
Analyzing this data, satellite engineers can design their satellites to withstand the amount of solar radiation they are likely to encounter once in orbit, according to Goddard. Researchers also combine the observational data with models of the Earth’s nuclear dynamics to try to predict what the anomaly will do next.
“This is similar to how weather forecasts are produced, but we work with much longer time scales,” said Andrew Tangborn, a mathematician at Goddard’s Planetarium Geodynamics Laboratory, in the Goddard article.
Meanwhile, researchers outside NASA are working to understand the links between the motion of the outer core and the functions of the magnetic field it produces. Researchers from the University of Liverpool in England recently reported that volcanic rocks are made of lava that erupted long ago on the Atlantic island of St. Helena shows magnetic anomalies dating to between 8 million and 11.5 million years ago, suggesting that this area of the South Atlantic Anomaly has been unstable for millions of years.
Originally published on Live Science.
