Although the Earth’s Van Allen radiation belts were discovered over 50 years ago, the dominant processes responsible for relativistic electron acceleration, transport and loss remain poorly understood.
By analyzing data from NASA’s Van Allen probes, researchers from the University of Alberta, have identified the existence of a giant cosmic accelerator above the Earth.
A physicist Ian Mann, together with his colleagues at NASA and other institutes, have been able to measure and identify the “smoking gun” of a planetary scale process that accelerates particles to speeds close to the speed of light within the Van Allen radiation belt.
The twin Van Allen Probes were launched on August 30, 2012 into elliptical, near-equatorial orbits around the Earth. Remarkably, rather than seeing just the well-known two-belt structure, the mission found almost immediate evidence of the clear three-belt structure portrayed in green in this diagram. Credit: Andy Kale, University of Alberta
This natural space “synchrotron accelerator” has scales of hundreds of thousands of kilometers, dwarfing even the largest man-made similar accelerators such as the Large Hadron Collider at CERN, which has a circumference of only 27 kilometres.
This particle acceleration – deriving energy from solar flares or eruptions and carried through space on a solar wind – exists in the region of space dominated by the Earth’s magnetic field, where satellites fly, known as the magnetosphere, Mann said.
“The puzzle ever since their discovery has been how do the particles get accelerated up to nearly the speed of light?” said Mann.
Mann says this highly relativistic particle acceleration, which can damage satellites and pose a risk to astronauts during space weather storms, is akin to the relationship between a surfer and a wave, in that the particles repeatedly catch a “ride” on a wave that sends them rocketing around the planet.
As they circle the Earth, the particles may be picked up again by the same wave, which will boost its speed even further. The result is a perpetual cycle wherein the particles “get repeatedly accelerated by waves that are coherent on truly planetary scales spanning hundreds of thousands of kilometers,” Mann said.
“With this discovery, we’re starting to put the pieces together to understand how this radiation might be created and, therefore, understand how extreme the response to severe space storms might be.”
The discovery is an important step to understand space storms in order to protect man-made systems – on Earth and in space – from potential damage from space storms and severe space weather.
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