Using data from NASA’s Van Allen Probes, scientists have discovered a massive particle accelerator in the heart of one of the harshest regions of near-Earth space, the super-energetic, charged particles surrounding the globe known as the Van Allen radiation belts.
Local bumps of energy kick particles inside the belts to ever-faster speeds, much like a well-timed push on a moving swing. Knowing the location of the acceleration within the radiation belts will help scientists improve predictions of space weather, which can be hazardous to satellites near Earth. The results were published earlier this year in the journal Science.
The twin Van Allen Probes fly straight through this intense area of space. By taking simultaneous measurements with their instruments, the satellites were able to distinguish between two broad possibilities of what accelerates the particles to such amazing speeds, deducing that the particles are undergoing local acceleration, rather than radial acceleration.
The data showed an increase in energy that started right in the middle of the radiation belts and gradually spread both inward and outward, which implies a local acceleration source. The research shows this local energy comes from electromagnetic waves coursing through the belts, tapping energy from other particles residing in the same region of space.
The challenge for scientists now is to determine which waves are at work. The Van Allen Probes, which are designed to measure and distinguish between many types of electromagnetic waves, will tackle this task, too.