Data from the European Space Agency's (ESA) Cluster mission has provided a recording of the 'eerily disturbing' sound the Earth makes when it is hit by a solar storm.
The song comes from waves produced in the Earth's magnetic field by the collision of the storm– the storm itself being the explosion of electrically charged particles from the atmosphere of the Sun.
A team led by former ESA researcher Lucille Turc who is now based at the University of Helsinki, Finland made the discovery after examining data from the Cluster Science Archive. The Cluster has four spacecraft that orbit Earth in formation, analyzing the planet's magnetic environment and its interactions with the solar wind.
The spacecraft repeatedly fly through the foreshock, the first region that particles come across when a solar storm hits the Earth.
The team found that from 2001 to 2005, the spacecraft flew through six collisions, recording waves that were produced. The findings showed that during the collision, the foreshock is triggered to release magnetic waves that are more complex than expected.
"Our study reveals that solar storms profoundly modify the foreshock region," Turc said.
When the frequencies are converted into audible signals, they make an 'uncanny' song– something that seems like a sound effect from a science fiction movie.
"It's like the storm is changing the tuning of the foreshock," Turc explained. Once the storm hits the foreshock, the wave breaks into a network of various, higher frequencies.
The Vlasiator model performed simulations of the foreshock, demonstrating the intricate wave pattern that appears during solar storms. The changes in the foreshock can affect the way the solar storm is generated down to the surface of the Earth.
"We always expected a change in frequency but not the level of complexity in the wave," Turc added.
Solar storms are part of the weather in space. While the solar wind is always blowing, eruptions of energy near the Sun's surface propagate turbulence and gusts that produce solar storms.
Studying space weather has increasingly become more significant because of the damaging effects solar storms can cause on sensitive electronics and technology on Earth and in space. ESA's upcoming Solar Orbiter mission set to launch in February 2020 will contribute to these studies.
"This is an excellent example of how Cluster continues to extend our knowledge of the Sun-Earth connection, even years after the original data was obtained," said Philippe Escoubet, ESA Project Scientist for Cluster.
"The results take us deeper into the details of fundamental magnetic interactions that take place across the universe."
"First Observations of the Disruption of the Earth's Foreshock Wave Field During Magnetic Clouds" – Turc, L. et al – Geophysical Research Letters. DOI: 10.1029/2019GL084437
The foreshock, extending upstream of Earth's bow shock, is a region of intense electromagnetic wave activity and nonlinear phenomena, which can have global effects on geospace. It is also the first geophysical region encountered by solar wind disturbances journeying toward Earth. Here, we present the first observations of considerable modifications of the foreshock wave field during extreme events of solar origin called magnetic clouds. Cluster's multispacecraft data reveal that the typical quasi‐monochromatic foreshock waves can be completely replaced by a superposition of waves each with shorter correlation lengths. Global numerical simulations further confirm that the foreshock wave field is more intricate and organized at smaller scales. Ion measurements suggest that changes in shock‐reflected particle properties may cause these modifications of the wave field. This state of the foreshock is encountered only during extreme events at Earth, but intense magnetic fields are typical close to the Sun or other stars.
Featured image credit: Vlasiator team, University of Helsinki
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