(Sen) - For centuries the dancing display of aurorae has both beguiled and mystified, but now scientists are one step closer to understanding the processes that drive these magical phenomena.
The aurora are created when solar winds, laden with charged particles interact with the Earth’s magnetic field and become channelled into the atmosphere. See Mark Thompson's guide to aurora.
What has been a mystery is the cause of the large scale acceleration of electrons that occurs in the Earth's magnetotail.
Now a team of researchers from the Massachusetts Institute of Technology (MIT) have published a paper explaining how the acceleration works. The research team, led by Jan Egedal, a professor of physics at MIT, used a powerful computer simulation to produce data to support Egedal's theory of the large scale acceleration.
The research explains how charged particles are being accelerated in Earth's magnetic tail, or magnetotail.
Artist's impression of the magnetosphere. Credit: NASA
The magnetotail is a region of the magnetosphere that has been stretched out into space by the solar wind. As it is stretched, the magnetic field stores energy (like a rubber band) and, when normal field lines reconnect, the energy is released – like snapping an elastic band.
This colossal release of energy accelerates the charged particles back towards Earth at great speed, where they smash into gas molecules in the upper atmosphere – creating the aurora.
Over 11 days, the motions of 180 billion simulated particles were mapped out by the MIT team using a supercomputer called Kraken. The complex simulations were created using data from spacecraft like the European Space Agency’s Cluster probes.
This "slingshot" theory had been considered impossible by some physicists because the magnetotail was thought to be too small. Plasma - electrically charged gas - should be a good conductor and prevent an electric field from being sustained in the magnetic field lines. But, according to the new study, such a field is just what’s needed to accelerate the electrons. According to the new simulation, the volume of space where such fields can build up can, in fact, be at least 1,000 times larger than the theorists had thought possible — and thus large enough to explain the observed electrons.
Aside from causing the aurora, these super energetic particles can damage spacecraft and affect communications on Earth, so understanding how they become accelerated is very important.
"These hot electrons can destroy spacecraft,” Professor Egedal says, which is why both the military and NASA “would like to understand this better.”
The work was supported by grants from NASA and the National Science Foundation.