A 60-Year-Old Mystery About The Van Allen Belts Has Been Solved

Scientists have solved a 60-year-old mystery about Earth’s Van Allen radiation belts, thanks to a tiny orbiting satellite.

Led by students from the University of Colorado Boulder and published in Nature, the study looked at the source of energetic electrons in Earth’s inner radiation belt, near its inner edge.

The Van Allen belts are two large belts of radiation that surround Earth. Since their discovery in 1958, no one had been sure where the high-energy electrons came from.

In this study, the researchers suggest they likely originate from supernovae. In a process called “cosmic ray albedo neutron decay” (CRAND), they suggest that cosmic rays from these explosive events enter Earth’s atmosphere and collide with neutron atoms.

In turn, this creates a “splash”, producing charged particles like electrons that are then trapped by Earth’s magnetic field. These are then locked into the Van Allen belts, leading to what we see today.

“We are reporting the first direct detection of these energetic electrons near the inner edge of Earth’s radiation belt,” said Professor Xinlin Li, the study’s lead author. “We have finally solved a six-decade-long mystery.”

The satellite on Earth before going to space. CU Boulder

Energetic electrons can pose a problem for astronauts on a spacewalk, while they can also damage satellites that are in orbit. Better understanding where they come from can help us forecast their arrival in near-Earth space.

The finding was made possible thanks to a CubeSat called the Colorado Student Space Weather Experiment (CSSWE). CubeSats are small satellites about the size of a loaf of bread. This particular satellite was launched back in September 2012 on an Atlas V rocket.

On board the satellite was an instrument called the Relativistic, Electron and Proton Telescope. As the CubeSat orbited Earth out to 777 kilometers (483 miles) above the surface, it collected data on the interaction between our atmosphere and the Van Allen belts. The satellite ran out of power in December 2014.

“This is really a beautiful result and a big insight derived from a remarkably inexpensive student satellite, illustrating that good things can come in small packages,” said study co-author Daniel Baker.

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