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Earth’s magnetic song recorded for the first time during a solar storm

by European Space Agency

Earth’s magnetic song recorded for the first time during a solar storm
In this image, Earth is the dot to the left of the image and the large arc around it is our planet’s magnetic bow shock. The swirling pattern to the right is the foreshock region where the solar wind breaks into waves as it encounters reflected particles from the bow shock. The image was created using the Vlasiator model, a computer simulation developed at the University of Helsinki to study Earth’s magnetic interaction with the solar wind. Credit: Vlasiator team, University of Helsinki

Data from ESA’s Cluster mission has provided a recording of the eerie “song” that Earth sings when it is hit by a solar storm.

The song comes from waves that are generated in the Earth’s magnetic field by the collision of the storm. The storm itself is the eruption of electrically charged particles from the sun’s atmosphere.

A team led by Lucile Turc, a former ESA research fellow who is now based at the University of Helsinki, Finland, made the discovery after analyzing data from the Cluster Science Archive. The archive provides access to all data obtained during Cluster’s ongoing mission over almost two decades.

Cluster consists of four spacecraft that orbit Earth in formation, investigating our planet’s magnetic environment and its interaction with the solar wind—a constant flow of particles released by the sun into the Solar System.

As part of their orbits, the Cluster spacecraft repeatedly fly through the foreshock, which is the first region that particles encounter when a solar storm hits our planet. The team found that in the early part of the mission, from 2001 to 2005, the spacecraft flew through six such collisions, recording the waves that were generated.

The new analysis shows that, during the collision, the foreshock is driven to release magnetic waves that are much more complex than first thought.PausePlay% buffered00:0000:13UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreenPlayThe magnetic waves measured by ESA’s Cluster mission in the magnetic foreshock above Earth – the first region of our planet’s magnetic environment that solar wind particles encounter – during calm space weather conditions. The video contains a ‘sonification’ of the magnetic waves in the undisturbed foreshock, obtained by transforming the frequencies of these magnetic waves into audible signals. In the undisturbed foreshock, the sounds are very low pitch and monotonous. Credit: ESA/Cluster; L. Turc et al. (2019); Audio: Martin Archer, Queen Mary University of London, CC BY-SA 3.0 IGO

“Our study reveals that solar storms profoundly modify the foreshock region,” says Lucile.

When the frequencies of these magnetic waves are transformed into audible signals, they give rise to an uncanny song that might recall more the sound effects of a science fiction movie than a natural phenomenon.

In quiet times, when no solar storm is striking the Earth, the song is lower in pitch and less complex, with one single frequency dominating the oscillation. When a solar storm hits, the frequency of the wave is roughly doubled, with the precise frequency of the resulting waves being dependent on the strength of the magnetic field in the storm.

“It’s like the storm is changing the tuning of the foreshock,” explains Lucile.

And it doesn’t stop there because not only does the frequency of the wave change but it also becomes much more complicated than the single frequency present in quiet times. Once the storm hits the foreshock, the wave breaks into a complex network of different, higher frequencies.

Computer simulations of the foreshock, performed using a model called Vlasiator, which is being developed at the University of Helsinki, demonstrate the intricate wave pattern that appears during solar storms.