Washington: Scientists have explained the unprecedented behaviour of a previously unknown third radiation ring that made a brief appearance between the inner and outer rings of Van Allen radiation belts in September 2012 and persisted for a month.
In the new research, UCLA space scientists have revealed that the extremely energetic particles that made up the third ring, known as ultra-relativistic electrons, are driven by very different physics than typically observed Van Allen radiation belt particles.
The region the belts occupy - ranging from about 1,000 to 50,000 kilometers above the Earth`s surface - is filled with electrons so energetic they move close to the speed of light.
Yuri Shprits, a research geophysicist with the UCLA Department of Earth and Space Sciences, said that in the past, scientists thought that all the electrons in the radiation belts around the Earth obeyed the same physics, but the recent study shows that radiation belts consist of different populations that are driven by very different physical processes.
"The velocity of ultra-relativistic electrons, which made up the third ring and are present in both the outer and inner belts, is very close to the speed of light, and the energy of their motion is several times larger than the energy contained in their mass when they are at rest," Adam Kellerman, a staff research associate in Shprits` group, said.
Kellerman asserted that the distinction between the behaviour of the ultra-relativistic electrons and those at lower energies was key to the study.
Shprits and his team found that on Sept. 1, 2012, plasma waves produced by ions that do not typically affect energetic electrons "whipped out ultra-relativistic electrons in the outer belt almost down to the inner edge of the outer belt."
Only a narrow ring of ultra-relativistic electrons survived this storm. This remnant formed the third ring.
After the storm, a cold bubble of plasma around the Earth expanded to protect the particles in the narrow ring from ion waves, allowing the ring to persist.
Shprits` group also found that very low-frequency electromagnetic pulsations that were thought to be dominant in accelerating and losing radiation belt electrons did not influence the ultra-relativistic electrons.
Shprits, who was honoured by President Obama last July with a Presidential Early Career Award for Scientists and Engineers, asserted that the Van Allen radiation belts can no longer be considered as one consistent mass of electrons since they behave according to their energies and react in various ways to the disturbances in space.
The study was published in the journal Nature Physics.