Academy Fellow Lucile Turc from the University of Helsinki is the head of an international group of researchers that uncovered the ‘new songs’ of the magnetic field. The researchers discovered the surprising phenomenon in certain parts of the magnetic field at some points of time, as they simulated the conditions and analysed the data produced by satellites.
Satellites in the collision between solar storm and magnetic field
The four Cluster Mission satellites of the European Space Agency (ESA) are orbiting Earth and gathering data on its magnetic fields and interaction with solar wind and storms. The researchers received the data gathered by the satellites over almost two decades.
The satellites frequently also fly into the area where solar wind collides with Earth’s magnetic field. The researchers found that, in the years 2001-2005, the satellites had crossed this area, called the foreshock, six times during solar storms, and recorded the waves in the magnetic field that were caused by the collision.
Solar storms are explosive eruptions of particles in the more even flow of electrically charged particles, i.e. solar wind, emanating from the Sun. When they reach the magnetic field protecting Earth, they give rise to beautiful Auroras but at the same time, cause surprising disturbances in the magnetic field.
‘Our study reveals that solar storms profoundly modify the foreshock region,’ says Lucile Turc.
From low and even to high-pitched and complex
When the frequencies of the waves are converted into sound, they produce a clear, chirping song. In calmer periods, when solar storms are not impacting Earth, the melody is low and even. Then, the vibration is dominated by one frequency. In the impact of a solar storm, the frequency approximately doubles, depending on the strength of the magnetic field.
‘It’s as if the solar storm was tuning the song of this part of space,’ says Turc, smiling.
The storm is not just adjusting the pitch of the song. Turc describes how it is like the solar storm is breaking up the wave of the magnetic field into a network of complex and high-pitched waves.
Predicted by computer simulation
A large part in the research is played by computer simulations based on the Vlasiator model, developed at the University of Helsinki, with which the researchers were able to describe the intricate wave pattern.
In fact, there were indications of the wave network from the first analysis of Vlasiator runs. These results were published in 2018 in the Journal of Geophysical Research. The analysis showed that the waves may become more complex during solar storms. However, the runs represented idealised conditions, so the status during a real solar storm still had to be verified.
The research published in Geophysical Research Letters will improve the predictability of the conditions in inner space, i.e. space weather. The predictions will also help protect sensitive instruments from disturbances in the magnetic field, which may endanger many vital devices, such as communication satellites and power-distribution networks..
The newest publication in the Geophysical Research Letters: First observations of the disruption of the Earth's foreshock wave field during magnetic clouds
The publication in the journal Geophysical Research in 2018: Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations
Listen to sound files, where the frequencies of the magnetic field waves have been converted into sound signals on ESA’s soundcloud site.