England (Commonwealth Union) – The German physicist Heinrich Rudolf Hertz displayed the existence of the waves predicted by Maxwell by forming radio waves in the laboratory back in 1887. Magnetic waves can be divided into seven types of waves, namely radio waves, microwaves, infrared, visible, ultraviolet, x-ray and gamma rays.
New research with the participation of the University College London (UCL) has revealed the way magnetic waves have their transmission past a standing shock wave, referred to as the bow shock, that forms ahead of Earth due to the the solar wind hitting our magnetic bubble known as the magnetosphere.
Shock waves take place in air when a plane moves quicker than the speed of sound and also occur in plasma which is a 4th state of matter that consists of 99 percent of the visible Universe in space. Shock waves have been assumed to speed up particles in supernovae which is the explosions of stars as well as in the jets released distantly into space from black holes. The new research, published in the journal Nature Physics, had the global research team explore magnetic waves that take place ahead of the Earth’s shock which is the bow shock, referred to as foreshock waves.
These waves are formed by particles bouncing off the shock and moving back towards the Sun. A computer model was applied that was known as Vlasiator, to simulate the physical methods taking place in the transmission from these waves, having waves on the other side of the shock with almost indistinguishable features as in the foreshock. The researchers then verified the availability of these waves making use of observational data obtained from NASA’s Magnetospheric Multiscale (MMS) mission.
The Co-author Dr Daniel Verscharen of the UCL Mullard Space Science Laboratory, who is an internationally leading expert in analyzing plasma waves and whose code was applied to interpret the MMS data, said: “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, it is a universal process occurring throughout the Universe. We cannot send a spacecraft to a supernova – so we are lucky to be able to study plasma shock waves in our own cosmic neighbourhood.”
Since the 1970s, space scientists had theorized the capability of magnetic waves to pass via the shock and come into our magnetosphere. The proof for this appears from magnetometers finding oscillations in the Earth’s magnetic field at the same period as the waves that are produced ahead of the Earth’s magnetosphere. However, many major hurdles have blocked their path, where the 1st the waves must move across the shock, which slows down the solar wind prior to it hitting the Earth’s magnetic field at supersonic speed, followed by a traverse of a turbulent region of space before finally moving into the magnetosphere of earth.
“At first, we thought that the initial theory proposed in the 1970s was correct: the waves could cross the shock unchanged. But there was an inconsistency in the wave properties that this theory could not reconcile, so we investigated further,” explained Dr Lucile Turc, who is the lead author from the University of Helsinki, Finland and further said “Eventually, it became clear that things were much more complicated than it seemed. The waves we saw behind the shock were not the same as those in the foreshock, but new waves created at the shock by the periodic impact of foreshock waves.”
The numerical model also highlighted that the waves were only identifiable in a narrow section behind the shock, and that they could easily be out of sight by the turbulence in this region, possibly indicating why they were not noticed before.
