MessageToEagle.com - Scientists have long believed that the Van Allen radiation belts in in the Earth's
upper atmosphere discovered in 1958, consisted of two doughnut-shaped rings of highly charged particles -
an inner ring of high-energy electrons and energetic positive ions, and an outer ring of high-energy electrons.
This narrow ring had briefly circled the Earth between the inner and outer rings in September 2012 and
then almost completely disappeared.
A diagram showing Earth's Van Allen radiation belts together with a more recently discovered belt that contains trapped interstellar matter.
Credit: NASA/Van Allen Probes/Goddard Space Flight Center
How did this temporary radiation belt appear and dissipate?
In new research funded by the NASA, which launched the twin Van Allen probes in the summer of 2012, the
radiation belt group in the UCLA Department of Atmospheric and Oceanic
Sciences explains the development of this third belt and its decay over a period of slightly more than four weeks.
By performing a "quantitative treatment of the scattering of relativistic electrons by electromagnetic whistler
mode waves inside the dense plasmasphere," the investigators were able to account for the "distinctively slow
decay of the injected relativistic electron flux".
The experiment demonstrates why this unusual third radiation belt is observed
only at energies above 2 mega-electron-volts.
Click on image to enlarge
A graphic depicting the twin Van Allen Probes in orbit within Earth's magnetic field. Credit: JHU/APL
Understanding the processes that control the formation and ultimate loss of such relativistic electrons is a
primary science objective of the NASA Van Allen Probe Mission and has important practical applications, because
the enormous amounts of radiation the Van Allen belts generate can pose a significant hazard to satellites and
spacecraft, as well to astronauts performing activities outside a spacecraft.