University of California, Los Angeles (UCLA) scientists have successfully modeled and explained what they consider to be a third radiation ring, discovered back in September of last year, sandwiched between the two existing Van Allen radiations belts.
Van Allen Radiation Belts
Van Allen radiation belts consist of highly charged, energetic particles, fixed around Earth by the planet’s magnetic field. These particles are primarily protons and electrons, with the radiation belts lying along the Earth’s magnetic equator.
Two of these radiation belts were first discovered by Dr. James Van Allen and his team, based at the University of Iowa, following the deployment of the United States’ first artificial satellite, called Explorer I.
The outer belt extends a distance of approximately 13,000 to 60,000 kilometers beyond the Earth’s surface, and comprise mostly of highly energetic electrons and protons. Scientists hypothesize that this apparent mixture of particles is evidence that they are derived from multiple sources.
The inner belt extends to an altitude of between 500 to 4,000 miles above the Earth’s surface.
However, during last year, a third, narrow Van Allen radiation belt was exposed between the afore-mentioned inner and out rings. The ring was witnessed for one month, before disappearing.
UCLA scientists set about producing models to explain this third ring, establishing that the electrons present within this newly discovered region are subject to physics that differs from those perceived in other belts. The third belt is 1,000 to 50,000 kilometers above the Earth’s surface, constituting “ultra-relativistic” electrons that whizz around at speeds close to that of light.
A research geophysicist, Yuri Shprits, who works with the Department of Earth and Space Sciences, explains how most scientists thought electrons obeyed the same laws of physics uniformly, across the entirety of the Van Allen radiation belts. According to Shprits, the situation appears to have changed:
“We are finding now that radiation belts consist of different populations that are driven by very different physical processes.”
Shprits published his findings, alongside his colleagues, in the journal Nature Physics. The group conducted simulations, using a model of Earth’s Van Allen radiation belts between August 2012 and October 2012. The simulation implemented the physics of ultra-relativistic electrons and the weather conditions of space to see if their models were in line with observations witnessed by NASA; according to Dmitriy Subbotin, one of Shprits’ former graduates, there was a “remarkable agreement” between the two, proving their model’s worth.
Van Allen belts represent considerable risk to today’s orbiting satellite technology. The belts consist of highly penetrating radiation, which eventually inflict damage to delicate internal circuitry.
Whitney Lohmeyer, of the Department of Aeronautics and Astronautics at MIT, recently published a study in Space Weather, demonstrating the impact of space weather conditions on satellite communications. The group showed that “… high-energy electron activity” damaged the amplifiers, and were responsible for most of the glitches witnessed between 1996 and 2012.
Meanwhile, Shprits suggests that the hazards imposed on spacecraft and satellite technology varies from mild anomalies to full blown, catastrophic failures within essential craft. He speculates that a better understanding of this damaging radiation could yield strategies that could better safeguard astronauts and equipment in space.
According to Adam Kellerman, a staff research associate working with Shprits, the ultra-relativistic electrons within the Van Allen radiation belts are capable of passing through the protective shielding of these expensive satellite technologies, with the energy of the particles’ motion several times the magnitude of the energy contained in their mass when not moving.
According to Shprits and Kellerman, the third ring was established by a plasma wave, which “whipped out” the electrons from the outer belt; only a very narrow slither of ultra-relativistic electrons were reported to have endured the violent storm.
In concluding their findings, Shprits indicates that the electrons can no longer be viewed as “… one consistent mass of electrons,” and respond to different space phenomena in various ways, depending upon their energies, and occupy a number of spatial structures.
Although the researchers’ models stack up with NASA’s observations, the team admit that more needs to be done to explain where the high-energy particles originate and how they are accelerated to such extraordinary speeds, as well as the dynamics of different storms and how they interact with Van Allen radiation belts.
By: James Fenner