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article imageScientists say they solved the mystery of northern lights

By JohnThomas Didymus     Feb 27, 2012 in Science
Scientists say they have solved the mystery of the origin of the energetic particles that cause Earth's northern and southern lights, also known as aurora. The problem has puzzled scientists for decades.
Auroras are natural light displays in the sky, especially in the Arctic and Antartic regions caused by collision of energetic electrons with atoms in the high altitude atmosphere (or thermosphere). The electrons are assumed to originate in the magnetosphere and solar wind and are directed by the Earth's magnetic field into the atmosphere. But scientists have puzzled over which region of the magnetosphere the electrons originate and are uncertain that there is enough volume of space in the magnetosphere to accelerate the electrons.
R&D Magazine reports that Jan Egedal, an associate professor of physics at Massachusetts Institute of Technology (MIT) and researcher at the Plasma Science and Fusion Center, working with MIT graduate student Ari Le, and with William Daughton of the Los Alamos National Laboratory (LANL), say they have solved the problem.
According to the scientists, electrons which cause the auroras are accelerated to very high speeds in a region of the Earth's magnetosphere called the magnetotail.
The scientists claim that the region provides enough volume of space to generate accelerated electrons, being 1,000 times larger than scientists had previously suspected.
Space.com reports that lead author Egedal, said: "People have been thinking this region is tiny...we’ve shown it can be very large, and can accelerate many electrons."
Red and green Auroras  Norway.
Red and green Auroras, Norway.
Frank Olsen
Egedal and his colleagues, according to Space.com, analyzed data gathered from spacecrafts, including the European Space Agency's four Cluster probes. They also did simulations using a supercomputer called Kraken at the U.S. Department of Energy's Oak Ridge National Laboratory in Tennessee.
The team used the kraken supercomputer to simulate particles in space and show how auroras are generated. According to R&D Magazine, the simulation showed that an active region in the Earth's magnetotail, where "reconnection" events take place is roughly 1,000 times larger than was thought. Thus, there is sufficient volume of space in the magnetotail to account for the numbers of accelerated electrons detected by spacecraft missions. The study concluded that the electrons were being accelerated in the magnetotail pushed far into space. Streams of charged particles called solar wind stretch the Earth's magnetic lines making them store energy (like rubber band being stretched). Release of the energy, when "parallel field lines reconnect," propels electrons towards our planet at very high speeds. When the accelerated electrons collide with molecules in the Earth's upper atmosphere, visible phenomenon of northern and southern lights are generated.
Aurora australis
Aurora australis
Fir0002
Space.com reports, however, that this theory had been challenged by physicists who believe that the active magnetotail region is not big enough to generate the numbers of electrons observed entering the Earth's atmosphere.
R&D Magazine reports Egedal had proposed a theory to explain the acceleration of electrons in the Earth's magnetotail before data was obtained from the computer simulation. But now with supporting evidence from computer simulation, Egedal says: "It used to be people said this was a crazy idea. I don't get that anymore."
aurora australis
aurora australis
Mozasaur
Edgal and his co-workers showed that the magnetotail region is big, about 1,000 times bigger than was thought.
Space.com reports that besides the fact of the beautiful lights display, the auroras can damage spacecraft. This is why a better understanding of its origin and behaviour is important to scientists because it may help in developing methods for protecting spacecraft.
The study is published in the journal Nature Physics.
More about Northern lights, Aurora, earth's magnetosphere, Mit
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