Dec. 20 () –
Scientists have shown for the first time how magnetic waves are transmitted through the arc shock that forms in front of the Earth when the solar wind hits our magnetic bubble.
Shock waves occur in air when a plane travels faster than the speed of sound, and they also occur in plasma (a fourth state of matter that makes up 99% of the visible Universe) in space. Shock waves are thought to accelerate particles in supernovae (exploding stars) and in jets launched into space by black holes.
For the new study, published in Nature Physics, The international team of researchers looked at the magnetic waves that occur before the Earth collides, known as advanced shock waves. They are created by particles that bounce off the shock wave and head towards the Sun.
They used a computer model, Vlasiator, to simulate the physical processes involved in transmitting these waves, finding waves on the other side of the shock with nearly identical properties to advanced waves. They then confirmed the presence of these waves using observational data from NASA’s Magnetospheric Multiscale (MMS) mission.
Co-author Dr. Daniel Verscharen, from University College London, a world expert in plasma wave analysis and whose code was used to interpret the MMS data, stated it’s a statement: “Shock waves in plasma are much more difficult to understand than when they occur in air. There is a lot of space between the particles and collisions between them are rare.”
“However, this is a universal process that occurs throughout the Universe. We cannot send a spaceship into a supernova, so we’re lucky to be able to study plasma shock waves in our own cosmic neighborhood.“.
Since the 1970s, space scientists have theorized that magnetic waves could pass through the shock and enter our magnetosphere. Proof of this are the magnetometers that detect oscillations in the Earth’s magnetic field. in the same period as those waves that form in front of the terrestrial magnetosphere.
However, several major obstacles stand in their way: first, the waves must pass through the shock wave, which slows down the solar wind before it hits Earth’s magnetic field at supersonic speeds; they must then pass through a turbulent region of space (magnetosphere), before finally entering Earth’s magnetosphere.
In the words of Dr. Lucile Turc, lead author, from the University of Helsinki: “At first, we thought that the initial theory proposed in the 1970s was correct: the waves could go through the shock unchanged. But there was an inconsistency in the properties of waves that this theory could not reconcile, so we investigated further.”
“Eventually, it became clear that things were much more complicated than they seemed. The waves we were seeing behind the crash were not the same as those from the previous crash, but new waves created in the shock by the periodic impact of the waves of the previous shock”.
The numerical model also indicated that these waves could only be detected in a narrow region behind the shock, and could be easily hidden by turbulence in this region. This probably explains why they had not been observed before.
Although waves from advanced waves play only a limited role in space weather on Earth, they are of great importance for understanding the fundamental physics of our universe.
