A 60-year-old mystery regarding the source of some energetic and potentially damaging particles in the Earth’s radiation belts has been solved, using data from a student operated shoebox-sized satellite. The results indicate energetic electrons in Earth’s inner radiation belt – primarily near its inner edge – are created by cosmic rays born from explosions of supernovas, said Professor Xinlin Li from University of Colorado at Boulder in the US. Earth’s radiation belts, known as the Van Allen belts, are layers of energetic particles held in place by the planet’s magnetic field. The team showed that during a process called “cosmic ray albedo neutron decay” (CRAND), cosmic rays entering Earth’s atmosphere collide with neutral atoms, creating a “splash” which produces charged particles, including electrons, that become trapped by Earth’s magnetic fields. The findings have implications for understanding and better forecasting the arrival of energetic electrons in near-Earth space, which can damage satellites and threaten the health of space-walking astronauts, said Li.
“We are reporting the first direct detection of these energetic electrons near the inner edge of Earth’s radiation belt,” said Li, lead author of the study published in the journal Nature. “We have finally solved a six-decade-long mystery,” said Li. Soon after the discovery of the Van Allen radiation belts in 1958, both American and Russian scientists concluded that CRAND was likely the source of high-energy protons trapped in Earth’s magnetic field. However, over the intervening decades, no one successfully detected the corresponding electrons that should be produced during the neutron decay.
The CubeSat mission, called the Colorado Student Space Weather Experiment (CSSWE), houses a small, energetic particle telescope to measure the flux of solar energetic protons and Earth’s radiation belt electrons. Launched in 2012, CSSWE has involved more than 65 CU Boulder students and was operated for more than two years from a ground station they built on the roof of a building on campus. “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 Daniel Baker, co-author of the study.