An evolving dent in Earth's magnetic field, known as the South Atlantic Anomaly (SAA), is posing serious threats to satellites passing through the region.

While Earth's magnetic field acts as a shield against charged particles from the Sun, the SAA creates a weak spot in the field, allowing particles to get closer to the surface, resulting in the risk of knocking out onboard computers and interfering with the data collection of satellites passing through the region.

Hence, NASA scientists have been keeping track of the anomaly, observing and modeling it to predict future changes that can pose challenges to satellites and humans in space.

South Atlantic Anomaly

Located over South America and the southern Atlantic Ocean, the SAA does not currently create visible impacts on daily life on the surface.

However, recent observations and forecasts show that the region is expanding westward and continuing to weaken in intensity. It is also splitting into two lobes, presenting more challenges for satellites.

The SAA arises from two features of Earth's core: The tilt of its magnetic axis, and the flow of molten metals within its outer core, according to NASA.

The core magnetic field is not perfectly aligned through the globe, nor is it perfectly stable, and it fluctuates in space and time due to changing core motion.

NASA notes that the Sun emits particles and magnetic fields called the solar wind and coronal mass ejections that can become trapped in two donut-shaped belts around Earth called the Van Allen Belts.

When a strong storm of particles from the Sun reaches Earth, the Van Allen belts can become highly energized and the magnetic field can be deformed, giving way to the charged particles entering the atmosphere. This can be harmful to low-Earth orbit satellites that pass through the SAA.

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Weakening Dominance

Operators of satellites commonly shut down non-essential components as they pass through the SAA to avoid losing instruments or an entire satellite.

Terry Sabaka, a geophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said that the magnetic field is actually a superposition of fields from many current sources, with the bulk of the field coming from the core.

Weijia Kuang, a geophysicist, and mathematician in Goddard's Geodesy and Geophysics Laboratory, said that the observed SAA can be interpreted as a consequence of the weakening dominance of the dipole field in the region.

"More specifically, a localized field with reversed polarity grows strongly in the SAA region, thus making the field intensity very weak, weaker than that of the surrounding regions," Kuang said.

The SAA is of interest to NASA's Earth scientists who monitor the changes in magnetic field strength there, both for how such changes affect Earth's atmosphere and as an indicator of what's happening to Earth's magnetic fields deep inside the globe.

The evolving changes in the field that happen on a similar timescale to the convection of metals in the outer core provide scientists with new clues to unravel the core dynamics that drive the geodynamo.

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