Understanding the nature of these radiation belts and how they swell and shrink over time is an integral part of interpreting, and perhaps someday predicting, the space weather that surrounds our planet. Such space weather can, among other things, cause complications in electronics systems aboard satellites we depend on for communications and GPS.
The discovery of the radiation belts was the first discovery of the space age, observed in 1958 by the Explorer I spacecraft. Scientists soon realized that the belts can change shape in concert with incoming disturbances from the sun, sometimes quite dramatically. In
"The Van Allen Probes observations challenged our current views on the physics of the radiation belts," said
So scientists began to work on new models to explain this new set of observations. The Van Allen Probes can measure the widest range of energies and particle types ever observed. Therefore, there were accurate measurements of particles in this narrow ring - moving up to 99.9 percent of the speed of light - which could shed light on physical processes never before seen.
"When I started in space sciences, we didn't even look at such energetic particles, as we were not sure that we could trust observations at these energies," said Dmitry Subottin, a co-author on the paper at
By comparing computer simulations of the belts with data from the Van Allen Probes, Shprits and his colleagues determined that one commonly understood method for how particles are accelerated to high energies did not work for these ultra-fast particles. The mechanism depends on one of the many unique and varied waves that can be present in an environment of charged particles, otherwise known as plasma, such as exists in the radiation belts. Waves known as Very Low Frequency Chorus waves move so that they can easily buffet particles in the belts up to higher speeds, much the way a perfectly timed push on a swing increases its speed. These same waves can be responsible for causing particles to precipitate down out of the belts into the atmosphere. These VLF Chorus waves affect fast electrons but not ultra-fast electrons. On the other hand, fast electrons in the belts are not affected by another wave called Electromagnetic Ion Cyclotron or
Another kind of VLF wave called Hiss is found inside this plasmapause boundary, and this wave does not strongly affect the ultra-fast particles that the Van Allen Probes observed residing in the persistent narrow ring. This explains why the narrow ring was stable for such a long time.
An earlier paper in Geophysical Review Letters, published
"The higher the energy, the longer the life time," said Thorne. "Our models show that if nothing happens to perturb the radiation belts, the highest energy electrons can stay for 100 days. In the
Thorne's model does not include
"The ultra-relativistic electrons of the third ring have so much energy that they are driven by very different physical processes," said Shprits. "Incorporating that information not only explains the unusual observation of the long-lived narrow middle ring, it opens up a new area of research for the ultra-relativistic particles."
Understanding which configurations and environments speed up these extremely fast particles helps with protecting spacecraft traveling through and near this region. Spacecraft can shield against particles - which can trip electronics systems inside satellites - up to a certain threshold speed, but such ultra-fast particles are able to travel through most shields. Knowing more about the radiation belts, and how different populations respond to the disturbances from the sun, can help satellite manufacturers protect future spacecraft from the effects of electrons within the Van Allen Belts.
Keywords for this news article include: Spacecraft, Electronics, Aerospace and Defense,
Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2013, NewsRx LLC
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