A rare space weather event of the kind that could damage future satellite-dependent technology such as power grids and communications networks occurred at just the right moment on Mar, 17, 2015, according to a paper by NASA scientists published in the Journal of Geophysical Research. The NASA-produced video below helps explain what they learned when one of their twin Van Allen research probes passed through a shockwave from a Coronal Mass Ejection (an explosion of solar matter from the sun).
Scientists still have much to learn about the Van Allen radiation belts, which were first discovered in the 1950's. The belts are enormous, donut-shaped rings of charged particles that circle magnetized planets like Earth. They contain particularly dangerous forms of radiation, held in place by the magnetic field surrounding the planet, and swell and shrink in response to changing conditions in space. This activity may play a role in protecting the Earth's inner atmosphere from radiation, but it also poses a threat to astronauts and spacecraft that orbit within the belts.
The effects of interplanetary shocks tend to be highly localized. If an astronaut or a spacecraft is not in exactly the right place when it happens, it may not register the event at all. Luckily, in this case the Van Allen probe was in exactly the right place. The March 2015 storm was the most dramatic event of its type in the last decade.
As the shockwave slammed into the outer radiation belt, the probe recorded a sudden pulse of electrons energized to extreme speeds – nearly as fast as the speed of light. The pulse of electrons was so short-lived that their energy dissipated within minutes. But the electrons left behind a very dynamic environment within the Van Allen belts, with electromagnetic waves lingering for days. Five days later – long after other effects of the storm had died down – the probes detected an increased number of electrons energized to even higher levels. Having such a big increase so much later demonstrates the unique energization processes following the storm. Electrons moving at this speed can knock out circuitry and badly damage living tissue.
"The shock injected – meaning it pushed – electrons from outer regions of the magnetosphere deep inside the belt, and in that process, the electrons gained energy," said Shri Kanekal, leading author of the paper and deputy mission scientist for the Van Allen Probes at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
As scientists gather data from such events, they can compare and contrast them, ultimately helping to create robust models of the little-understood processes occurring in the Van Allen radiation belts. This in turn will help us better map out space weather events and improve the way we respond to them, and how we design future satellites, spacecraft and space suits.
The research was published in the Journal of Geophysical Research.
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