Scientists have discovered that the ‘weak spot’ in Earth’s magnetic field is growing, allowing harmful radiation to get closer to our planet’s surface.
The region, known as the South Atlantic Anomaly (SAA), covers more than 4.3 million square kilometers across parts of Africa and South America and is moving westward.
The ‘dent’ allows harmful radiation particles from the sun to seep through the weak region of our planet’s magnetic field. NASA has warned that this could “disable onboard computers and disrupt data collection from satellites passing through them.”
The SAA has increased by seven percent and moved twelve kilometers to the west since experts first sounded the alarm in 2020.
Although scientists believe that the decreasing magnetic intensity of the SAA is still within the range of normal variation, recent studies have shown that it is beginning to split from a single blob into two distinct regions of minimal magnetic field strength.
Models predicting changes in the SAA suggest these divisions will continue from 2025 onwards, and scientists think this could pose additional challenges for satellite missions.
Researchers have speculated that the weakening is a sign that Earth is heading for a polar reversal that happens when the north and south poles switch places – and the last time this happened was 780,000 years ago.
They said that if the poles are in the process of reversing, it will happen over a period of several thousand years and it is unlikely that the field will disappear completely.
NASA has been monitoring the South Atlantic Anomaly, a weak spot in Earth’s magnetic field 40,000 miles above the Earth’s surface between South America and Southwest Africa.
Scientists first raised the alarm about the vulnerability in 2020, but new data shows it has increased by a further seven percent in the past four years
The cause of SAA lies deep within the earth’s surface.
“The magnetic field is actually a superposition of fields from many current sources,” geophysicist Terry Sabaka of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, explained in a 2020 report. statement.
While regions outside Earth contribute to the observed magnetic field, the primary source comes from within the planet.
The outer layer of the Earth’s core is made of molten iron and nickel and is located 3,000 kilometers below the surface.
These swirling metals act like a huge generator called the ‘geodynamo’, creating electric currents that produce the magnetic field.
But this movement is not constant. It fluctuates over time, and as a result, the Earth’s magnetic field fluctuates as well.
This, combined with the tilt of the planet’s magnetic axis, is what NASA says yields the SAA.
But scientists have also suggested that the SAA could be linked to a vast reservoir of dense rock known as the African Large Low Shear Velocity Province (LLSVP). The area of the anomaly appears to correspond to that of this geological region.
The magnetic field around our planet acts like a shield, capturing and repelling radiation particles from the sun. But the SAA allows radiation to get closer to the Earth’s surface
These researchers believe that the African LLSVP changes the flow of molten metal in the outer core below, which in turn changes the way the magnetic field behaves above this region, they explained in a 2017 paper for the conversation.
While much remains unknown about how the SAA came into being, recent studies have shed new light on how it is changing.
Tracking performed by small satellites known as CubeSats confirmed that the SAA does not stay stuck in one place, but rather drifts around.
Researchers have also found that the anomalous region splits into two, with each representing different centers of minimum magnetic intensity within the larger SAA.
And another study suggested that this phenomenon is actually a recurring event that may have affected Earth as far back as 11 million years ago.
If that turns out to be true, it would contradict the idea that the SAA is a precursor to the reversal of the Earth’s magnetic field.
This massive, developing vulnerability is a point of intrigue and concern for scientists, especially those at NASA whose satellites and orbital spacecraft could be significantly damaged by the SAA – including the International Space Station.
When these orbiters pass over the anomaly, satellites and spacecraft may experience short circuits and malfunctions.
That’s because the reduced strength of Earth’s magnetic field causes the orbiters to be hit by incoming solar radiation that disrupts technological systems.
Normally this only causes low level interference. But in extreme cases it can permanently damage critical hardware in an orbiter.
To prevent such damage, operators regularly disable spacecraft and satellite systems before entering the SAA.
The weakened field has been on the radar of experts for years; they know that it has lost nine percent of its intensity over the past 200 years.
It also appears to affect the strength of the southern aurora, a display of natural light in the sky over high-latitude areas of the Southern Hemisphere.
A study published in the journal Geophysical research letters found a ‘substantial weakening’ of magnetic fluctuations in the southern aurora in February, where it overlaps with the SAA.
This weakening is even visible to the naked eye, the study authors said Living Science.
They believe the anomaly’s weakened magnetic force reduces the amount of energy that solar particles can bring into Earth’s atmosphere — which causes the aurora — even by bringing more of these particles close to the surface.
To better understand how the SAA affects satellites and spacecraft in orbit, and how it influences geophysical phenomena such as the southern aurora, NASA scientists have been monitoring it for years.