A 60-year-old mystery
regarding the source of some energetic and potentially damaging particles in
Earth's radiation belts is now solved using data from a shoebox-sized satellite
built and operated by University of Colorado Boulder students. The results of
this research are very big for scientists and it will a lot help in
understanding more about Earth.
The results from the new
study 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 the study's lead author, Professor Xinlin Li of CU Boulder's
Laboratory for Atmospheric and Space Physics (LASP).
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| Dozens of CU Boulder students designed and built the CSSWE CubeSat satellite, which was used to study energetic particles in the Van Allen radiation belts. Credit: University of Colorado |
Earth's radiation belts,
known as the Van Allen belts, are layers of energetic particles held in place
by Earth'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, also a professor in CU-Boulder's
aerospace engineering sciences department. "We have finally solved a
six-decade-long mystery." A paper on the subject was published in the Dec.
13 issue of Nature. The study was funded primarily by the National Science
Foundation.
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. But 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 LASP building on
campus.
The instrument on CSSWE,
called the Relativistic, Electron and Proton Telescope integrated little
experiment (REPTile) is a smaller version of REPT, twin instruments developed
by a CU Boulder team led by LASP director and Nature paper co-author Daniel
Baker that were launched on NASA's 2012 Van Allen Probes mission.
"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 Baker. "It's a major discovery that has been there
all along, a demonstration that Yogi Berra was correct when he remarked 'You
can observe a lot just by looking.'"
"These results
reveal, for the first time, how energetic charged particles in the near-Earth
space environment are created," said Irfan Azeem, a program director in
the NSF's Division of Atmospheric and Geospace Sciences.
"The findings will
significantly improve our understanding of the Earth-space environment,"
Azeem said. "It's exciting to see NSF-funded CubeSats built by
undergraduate and graduate students at the center of a significant scientific
discovery."
Via Phys.org