July 25, 2013
Particle Accelerator Sits In Heart Of Van Allen Belts
Lee Rannals for redOrbit.com - Your Universe Online
New results from NASA's Van Allen Probes has determined the location of a particle accelerator in the heart of the Earth's Van Allen Radiation Belts.Scientists discovered a massive particle accelerator inside a super-energetic, charged particle region surrounding the globe. Much like pushing a moving swing, local bumps of energy kick particles inside the belts to ever-faster speeds. Scientists can use this new information to improve predictions of space weather.
"Until the 1990s, we thought the Van Allen belts were pretty well-behaved and changed slowly," says Geoff Reeves, lead author on the paper, which was published in the journal Science, and a radiation belt scientist at Los Alamos National Laboratory.
"With more and more measurements, however, we realized how quickly and unpredictably the radiation belts change. They are basically never in equilibrium, but in a constant state of change."
NASA launched twin Van Allen probes in August last year to try and understand how particles in the belt are accelerated to ultra-high energies. The probes make simultaneous measurements to help distinguish between two broad possibilities of what accelerates the particles to such amazing speeds.
Scientists theorized radial acceleration or local acceleration as possibilities for what could be kicking up the energy. In radial acceleration, particles would be transported perpendicular to the magnetic fields that surround Earth, while in local acceleration the particles would gain energy from a local energy source.
The team found that they could distinguish between these two theories when they observed a rapid energy increase in the radiation belts last October. They made measurements that showed an intensification in particle energy that started in the middle of the radiation belts and spread both inward and outward, as would be expected from a local acceleration scenario. The energy comes from electromagnetic waves coursing through the belts.
"These new results go a long way toward answering the questions of where and how particles are accelerated to high energy," said Mona Kessel, Van Allen Probes program scientist in Washington. "One mission goal has been substantially addressed."
Scientists now need to determine which waves are at work. The twin probes are designed to measure and distinguish between several types of electromagnetic waves, which will help scientists decipher the waves better.
In February the Van Allen probes helped scientists determine that there was a third radiation belt, leading to the revision of a 50-year-old theory.