January 21, 2025
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Earth sings in a mysterious chorus of waves – deep space sings too
Strange bursts of energy called chorus waves have been detected in deep space far from Earth, suggesting they could cause problems for long-distance space travel.

Momentary pulsations that ripple through Earth’s magnetic field, called “chorus waves,” are associated with auroras similar to this one observed from the International Space Station in low Earth orbit. But new results show that chorus waves can occur in deep space, far from our world, potentially posing a danger to interplanetary travel.
NASA/UPI/Alamy Stock Photo
Thousands of kilometers above our heads, two powerful radiation belts surround our world. Here, particles trapped in Earth’s vast magnetic field zip around at near-light speeds, fast enough to pose a serious danger to spacecraft and astronauts attempting to pass through them. is. Some of the most lethal particles, known as “killer electrons,” reach such high velocities by being accelerated by peculiar perturbations of the Earth’s magnetic field called chorus waves. Chorus waves are so named because their sound resembles the sound of birds chirping. It has long been thought that these chorus waves only occur near Earth and other planets. And while in principle avoiding such waves would allow for safer, less radiation-plagued space travel, such waves are far more prevalent in deep space than anyone realized. New research suggests it’s common.
writing in diary nature, Chengming Liu of China’s Beihang University and colleagues are using NASA’s Magnetospheric Multiscale (MMS) mission, a four-satellite mission launched in 2015 by NASA to study Earth’s magnetic field, to study the Earth’s magnetic field. They report that they have found waves. However, these waves were not approaching the Earth at all. Instead, they emerged at a distance of 165,000 kilometers (100,000 miles) from our planet. This is about three times as far from Earth as the chorus waves detected so far. As such, they are located at the tail end of our planet’s bubble-like magnetosphere, far from where many researchers thought they must have formed.
“This is a very important paper,” says James Birch of the Southwest Research Institute, principal investigator of the MMS mission and co-author of the study. “This could be happening almost anywhere in the universe where magnetic fields exist.”
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Listen to the chorus wave audio reconstruction here.
Chorus waves, and more specifically chorus waves in whistler mode, are both fascinating and confusing at the same time. These are small bursts of energy that last only a few tenths of a second, and when translated into audio, create an unusual “chirp” sound in frequency. “The sound is very similar to a bird call at dawn,” says Richard Horne, a space weather expert at the British Antarctic Survey who studies the phenomenon. “That’s where they get their name.” The small fluctuations we recognize as chorus waves are produced by plasma instabilities, an unstable distribution of charged particles flowing along the Earth’s magnetic field lines. Because they can interact with high-energy particles trapped in our planet’s geomagnetic grip, “in the late 1990s and early 2000s it was suggested that they played a major role in the formation of Earth’s radiation belts. “We realized that we were playing a role in this,” said Horne, a reviewer of the new paper. nature This is the person who wrote the commentary that accompanies the paper.
The discovery of chorus waves happened by chance, not in space, but on Earth, when radio operators during World War I heard chorus waves emanating from thunderstorms. “People were listening to enemy communications, but instead they heard this chorus of ‘birds,'” said Alison Jaynes, a space weather physicist at the University of Iowa who was not involved in the study. say. “It later turned out that they were hearing chorus waves produced by lightning.”
Since then, this wave has been found on all the other planets in the solar system with similar magnetic fields: Mercury, Mars, Jupiter, Saturn, Uranus, and Neptune. It has also been discovered on Venus, which has no magnetic field. There, it was formed from a temporary field formed by the solar wind blowing into the Earth’s atmosphere.
Taken together, the findings so far suggest fairly simple prerequisites for creating chorus waves. It is a dipole magnetic field with “north” and “south” orientation, like the ends of a bar magnet, which curves magnetic field lines around the planet. , Earth, etc. This curved dipole configuration causes chorus waves to propagate from pole to pole, producing a “chirp”. However, because they are far from Earth, the latest research shows that the chorus waves “remove some of the curvature component,” said Daniel Ratliff, a plasma physicist at Northumbria University in the UK who was not involved in the study. say. “You still get a very clear, rising tonal character.”
This points to another mechanism for chorus wave generation: a change in the frequency of the magnetic field. These frequency changes can generate fast electrons that move through the magnetic field with minimal curvature, thus producing chorus waves. “This paper suggests that the cause of chorus radiation is frequency fluctuations,” says Yoshiharu Omura of Kyoto University in Japan, who was not involved in the study. Still, Omura and Ratliff note that both processes may still play a role.
This alternative path is important because it means that chorus waves are not confined to the curved magnetospheres of planets and stars, but are free to form anywhere in space with a magnetic field. “The universe is full of high-energy particles (such as cosmic rays), which may be contributing to the particles already there,” Birch says. “If you try to go to Mars from Earth, you’ll need a lot of shielding (from radiation). This is a new source of energetic electrons that we didn’t know about that could occur anywhere. So it’s a good idea to look for it. It should be done.”
Liu and his team also found evidence of a related effect called the “electronic hole.” This is essentially a gap in the chorus waves that collect as electrons propagate along the Earth’s magnetic field. “The resonance creates waves that create holes like this,” Horn says. “And that’s an important observation,” made possible thanks to unique data obtained from the MMS mission.
Magnetic reconnection, the process by which the magnetic field lines of the Earth and the Sun snap and release a burst of radiation, is also thought to be related to chorus waves, with chorus waves essentially containing some of the high-energy particles that can be supercharged. supply. Liu’s results suggest that this process is occurring “at a considerable distance from Earth,” Omura says. This link could improve space weather forecasting by allowing scientists to more accurately predict the occurrence of chorus waves around Earth and other planets by carefully monitoring the incoming solar wind. It may mean that there is a possibility.
That means understanding chorus waves could be important to avoid doomed swan songs on future missions to the Moon, Mars, and other deep space destinations. “If you’re pumping electrons to very high energies, you want to know how many of these killer electrons are in the magnetosphere for human spaceflight or spacecraft assets,” Jaynes says. “Chorus waves are really important to understanding that.” Learning more about them may help us learn more about when it’s safe to fly through these regions of space. “We want to predict when and where they will occur, so we know when and where they might be too dangerous for the operation,” Ratliff said. Masu.