A growing dent in Earth’s magnetic field could impact satellites and spacecraft


A growing dent in Earth’s magnetic field over South America and the southern Atlantic Ocean could pose a risk to spacecraft and satellites.

This evolving weak spot in the magnetic field, called the South Atlantic Anomaly, is being monitored by NASA, but the space agency said it will not affect us here on Earth.

The magnetic field protects us, acting as a shield against the solar wind — stream of charged particles and radiation — that flows out from the sun. This field’s protection also extends to include satellites orbiting close to Earth.

But the South Atlantic Anomaly is allowing solar particles to get closer than before. Solar radiation could have a negative effect as satellites pass through this area, knocking out their computers and interfering with data collection, according to NASA.

The South Atlantic Anomaly, new data has also shown, is weakening and expanding westward. Moreover, it’s splitting into two lobes, rather than one large one, which will cause further headaches for managing satellite missions.

Across a host of research areas, NASA scientists are monitoring the anomaly to prepare for those challenges, as well as how it could affect humans in space.

Earth scientists at NASA are also monitoring the anomaly to see how these localized changes in the strength of the magnetic field could affect our atmosphere.

What harm can the anomaly cause?

If satellites traveling through this weak area in the magnetic field are hit by energized particles, they can short-circuit, glitch or even sustain permanent damage. So satellite operators regularly shut down satellite components when they travel through the anomaly so they don’t risk losing key instruments or the whole satellite.

The International Space Station also passes through the anomaly. While the astronauts are safe inside the station, instruments on the outside of it that collect data can experience issues.

In fact, the anomaly has been known to reset power boards on the Global Ecosystem Dynamics Investigation mission, or GEDI, installed on the outside of the station, as frequently as once a month.

While this causes no materialharm, it does result in a couple of hours of lost data each month, according to Bryan Blair, the mission’s deputy principal investigator and instrument scientist, and a lidar instrument scientist at Goddard.

What causes it?

Earth’s magnetic field is produced by its molten, iron-rich core, which is in a constant state of motion 1,800 miles below the surface. These motions act like a generator, which is known as the geodynamo, and the electric currents that the movements create produce the magnetic field, according to NASA.

The Earth’s North and South poles also have magnetic field lines extending out from them, but they aren’t perfectly aligned or stable.

The motions of the planet’s outer core are variable, causing fluctuations in the magnetic field, and the magnetic poles tilt and migrate. Together, these factors have helped create the South Atlantic Anomaly.

“The magnetic field is actually a superposition of fields from many current sources,” said Terry Sabaka, a geophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement.

A weak area in the magnetic field is more susceptible to close encounters with the solar wind, as well as coronal mass ejections, which are massive clouds of heated plasma and radiation expelled by the sun.

The Van Allen radiation belts, which surround Earth, are filled with charged particles and plasma. These belts, shaped like doughnuts, can usually trap and hold the particles and radiation in place so they essentially bounce off Earth’s magnetic field.

The belts are part of Earth’s magnetosphere, or the region of space where Earth’s magnetic field interacts with solar wind.

The closer of the two belts is 400 miles from Earth’s surface — a good distance to protect Earth and its satellites from radiation. It’s more stable than the outer belt, which fluctuates and is located 8,400 to 36,000 miles above Earth’s surface.

But there is a flip side to the Van Allen belts: More intense space weather generated by the sun, which are rare events,can actually energize the belts, deform the magnetic field and allow radiation and charged particles into our atmosphere.

Scientists are also studying particle radiation in the area where the anomaly is located using data collected by NASA’s Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) mission.

The mission operated between 1992 and 2012, and its data helped reveal that the anomaly is drifting in a northwestern direction, which means its location shifts as the geomagnetic field evolves.

“These particles are intimately associated with the magnetic field, which guides their motions,” said Shri Kanekal, a researcher in the Heliospheric Physics Laboratory at NASA Goddard, in a statement. “Therefore, any knowledge of particles gives you information on the geomagnetic field as well.”

Preparing for the future

Data from SAMPEX has been used to design satellites that are less susceptible to failure if they encounter an issue passing through the anomaly. The European Space Agency’s Swarm mission, launched in 2013, observes the Earth’s magnetic field.

Then, scientists on Earth can create models and understand its current state. Scientists at NASA like Sabaka and Weijia Kuang, who is a geophysicist and mathematician in NASA Goddard’s Geodesy and Geophysics Laboratory, combine data from different sources to forecast how rapid changes may occur in the magnetic field going forward.

These NASA team members have contributed to the International Geomagnetic Reference Field. This collaborative effort assists with research concerning topics as varied as the Earth’s core and the outer limits of the atmosphere, and models Earth’s magnetic field and its changes.

“This is similar to how weather forecasts are produced, but we are working with much longer time scales,” said Andrew Tangborn, a mathematician in Goddard’s Planetary Geodynamics Laboratory, in a statement.

Scientists at NASA will continue observing the South Atlantic Anomaly with future missions so they can make models and predictions, as well as better understand Earth’s core.

And missions like NASA’s Parker Solar Probe and the European Space Agency’s Solar Orbiter are helping us to understand the solar wind streaming toward Earth.

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