Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultra-fast Electrons Explain Third Radiation Ring Around Earth

25.09.2013
In the already complicated science of what creates – and causes constant change in – two giant doughnuts of radiation surrounding Earth, researchers have added a new piece of information: some of the electrons reach such enormous energies that they are driven by an entirely different set of physical processes. These results were published in a paper in Nature Physics on Sept. 22, 2013.

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.


In September 2012, NASA's Van Allen Probes observed the radiation belts around Earth had settled into a new configuration, separating into three belts instead of two. Scientists think the unusual physics of ultra-fast electrons within the belt helped cause the unusual shape.
Image Credit: NASA/Goddard Space Flight Center

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 February 2013, researchers announced observations from NASA's Van Allen Probes, showing a previously undetected configuration. The belts showed a distinct unusually narrow ring beyond the inner belt persisting for a month in September 2012 while additional particles funneled in to create a third, larger, outermost belt. This previously unknown configuration of three bands, changed what was previously understood about the belts and set people in search of new explanations.

"The Van Allen Probes observations challenged our current views on the physics of the radiation belts," said Yuri Shprits, a space scientist at the University of California in Los Angeles and first author of the Nature Physics paper. "In the past we made estimates and thought they looked reasonable. Now we know we need to understand each storm in much more detail, creating global models that can reconstruct what's happening at every level."

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 UCLA. "The Van Allen Probes measurements give us confidence that these observations were reliable."

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 EMIC waves, but this study showed just how strongly EMIC waves can affect the fastest moving particles. Indeed, the EMIC waves can help quickly deplete the most energetic particles, leaving behind only a narrow ring of radiation protected inside the boundary known as the plasmapause, as seen in the September 2012 event.

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 July 28, 2013, provided similar explanations for the persistence of the third ring. The researchers in that paper, led by Richard Thorne who is a radiation belt scientist at UCLA, used data from both the Van Allen Probes and from NASA's THEMIS mission to model just how long it would take high energy particles to decay in the presence of a kind of VLF wave known as plasmaspheric hiss. The process might take only a few days for the slower particles, but took much longer for higher energy ones.

"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 September 2013 event, another storm came along and wiped that ring out after about a month, but before that the particles in the ring decayed as we predicted."

Thorne's model does not include EMIC waves in its explanation for why the particles in the outer ring depleted so quickly in that particular event. This goes to show how many questions are left about the wide variety of processes and waves that can affect different particles in the belts.

"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.

For more information on the Van Allen Probes:
www.nasa.gov/vanallenprobes
For more information on the Van Allen Probes' view of a third radiation belt:
http://1.usa.gov/Z0pUQA

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.

Karen C. Fox | EurekAlert!
Further information:
http://www.nasa.gov
http://www.nasa.gov/content/goddard/ultra-fast-electrons-explain-third-radiation-belt/index.html#.UkH1FT-E5nk

More articles from Physics and Astronomy:

nachricht Midwife and signpost for photons
11.12.2017 | Julius-Maximilians-Universität Würzburg

nachricht New research identifies how 3-D printed metals can be both strong and ductile
11.12.2017 | University of Birmingham

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Midwife and signpost for photons

11.12.2017 | Physics and Astronomy

How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas

11.12.2017 | Earth Sciences

PhoxTroT: Optical Interconnect Technologies Revolutionized Data Centers and HPC Systems

11.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>