An illustration to explain the dynamics of the ultra-relativistic third Van Allen radiation belt, by Andy Kale. Credit: Andy Kale
Like a protective shield, the Earth’s magnetosphere absorbs and deflects plasma from the solar wind which originates from the Sun. When conditions are right, beautiful dancing auroral displays are generated. But when the solar wind is most violent, extreme space weather storms can create intense radiation in the Van Allen belts and drive electrical currents which can damage terrestrial electrical power grids. Earth could then be at risk for up to trillions of dollars of damage.
A new discovery shows for the first time how the puzzling third Van Allen radiation belt is created by a “space tsunami.” Intense so-called ultra-low frequency (ULF) plasma waves excited on the scale of the whole magnetosphere, transport the outer part of the belt radiation harmlessly into interplanetary space and create the previously unexplained feature of the third belt.
“Remarkably, we observed huge plasma waves,” says Prof Ian, University of Alberta. “Rather like a space tsunami, they slosh the radiation belts around and very rapidly wash away the outer part of the belt, explaining the structure of the enigmatic third radiation belt.” The research also points to the importance of these waves for reducing the space radiation threat to satellites during other space storms as well.
The Van Allen belts are regions within the magnetosphere where high-energy protons and electrons are trapped by Earth’s magnetic field. Known since 1958, these regions were historically classified into two inner and outer belts. However, in 2013, NASA’s Van Allen Probes reported an unexplained third Van Allen belt that had not previously been observed. This third Van Allen belt lasted only a few weeks before it vanished, and its cause remained inexplicable.
“We have discovered a very elegant explanation for the dynamics of the third belt,” says Mann. “Our results show a remarkable simplicity in belt response once the dominant processes are accurately specified.” Many of the services we rely on today, such as GPS and satellite-based telecommunications, are affected by radiation within the Van Allen belts. Radiation in the form of high-energy electrons, often called “satellite killer” electrons because of their threat to satellites, is a high profile focus for the International Living with a Star (ILWS) Program and international cooperation between multiple international space agencies. Recent socio-economic studies of the impact of a severe space weather storm have estimated that the cost of the overall damage and follow-on impacts on space-based and terrestrial infrastructure could be as large as high as $2 trillion USD.
Politicians are also starting to give serious consideration to the risk from space weather. The White House recently announced the implementation of a Space Weather Action Plan highlighting the importance of space weather research like this recent discovery. The action plan seeks to mitigate the effects of extreme space weather by developing specific actions targeting mitigation and promoting international collaboration.
http://phys.org/news/2016-06-space-tsunami-van-allen-belt.htmljCp
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