In space, no one can hear you screaming because the sound cannot travel in a vacuum. But if we convert electromagnetic activity to sound, it suddenly becomes a very noisy place. And our earth is no exception; specifically in and around the magnetic field generated by the molten core of the earth.
This barrier, called a magnetosphere, is considered to be one of the most important ingredients for a life supporting planet and protects us from the harsh radiation from the solar wind. And the stronger the wind, the higher the magnetosphere sings.
As charged particles from the solar wind current towards the magnetosphere, some are reflected from the shock region in front of the magnetic field back toward the sun. This "backsplash" then interacts with the solar wind that is still flowing in, generating plasma instabilities and resulting in magnetoacoustic waves.
Scientists on earth then translate these magnetoacoustic waves into sounds – strange chirps and whistles – to understand the dynamics of interactions between the solar wind and the magnetosphere.
For the first time, the song Earth and Sun has been recorded during a solar storm, when the solar wind blows most wildly and hardest into space.
Four orbiting spacecraft, collectively called the Cluster mission, performed by the European Space Agency, sampled six solar storms from the pre-shock – the region upstream of the Earth's arc shock, where the solar wind first buzzes against the Earth's magnetosphere.
Audio files from the electromagnetic waves reveal that the waves in the magnetosphere created by a solar storm are much more complex than previously thought.
"Our study reveals that solar storms are deeply modifying the pre-shock region," says physicist Lucile Turc at the University of Helsinki, Finland, who led an international research group. "It's like the storm is changing the attitude of the pre-shock."
As you hear in the video below, the magnetosphere is never silent. Particles and radiation always flow from the sun, giving a certain level of calm solar weather chirping.
During a solar storm – when a large-scale magnetic eruption takes place on the sun's surface and sends charged particles that plunge into space (and if it hits the earth, which often produces really beautiful auras) – things become much more dramatic.
During normal calm weather, the magnetosphere produces low-frequency waves, dominated by a single frequency. During a solar storm, the pressure from the solar wind that drives the frequency of the wave becomes much higher. In addition, a number of these higher frequency waves are overlaid in a complex network, rather than just a dominant frequency.
"We always expected a change in frequency, but not the level of complexity in the wave," Turc noted.
The arc shock, between the magnetosphere and the pre-shock, is a further barrier between the waves and the earth, but we know that the waves do not bounce back towards the sun – there is too much pressure from the solar wind.
Rather, these changes of the prechamber are propagated all the way down to the soil surface in a few minutes; or they can trigger fast jet jets in the magnetic shield causing geomagnetic interference, which in turn can affect communication and navigation equipment, and electrical systems
Turc and her team are now working to try to understand how these complex wave superpositions are generated.
The research has been published in Geophysical research letters.