Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NASA's Van Allen Probes Show How to Accelerate Electrons

16.07.2014

One of the great, unanswered questions for space weather scientists is just what creates two gigantic donuts of radiation surrounding Earth, called the Van Allen radiation belts. Recent data from the Van Allen Probes -- two nearly identical spacecraft that launched in 2012 -- address this question.

The inner Van Allen radiation belt is fairly stable, but the outer one changes shape, size and composition in ways that scientists don't yet perfectly understand. Some of the particles within this belt zoom along at close to light speed, but just what accelerates these particles up to such velocities?


NASA's Van Allen Probes orbit through two giant radiation belts surrounding Earth. Their observations help explain how particles in the belts can be sped up to nearly the speed of light.

Image Credit: NASA

Recent data from the Van Allen Probes suggests that it is a two-fold process: One mechanism gives the particles an initial boost and then a kind of electromagnetic wave called Whistlers does the final job to kick them up to such intense speeds.

"It is important to understand how this process happens," said Forrest Mozer, a space scientist at the University of California in Berkeley and the first author of the paper on these results that appeared online in Physical Review Letters on July 15, 2014, in conjunction with the July 18 print edition.

"Not only do we think a similar process happens on the sun and around other planets, but these fast particles can damage the electronics in spacecraft and affect astronauts in space."

Over the last few decades, numerous theories about where these extremely energetic particles come from have been developed. They have largely fallen into two different possibilities. The first theory is that the particles drift in from much further out, some 400,000 miles or more, gathering energy along the way. The second theory is that some mechanism speeds up particles already inhabiting that area of space. After two years in space, the Van Allen Probes data has largely pointed to the latter.

Additionally, it has been shown that once particles attain reasonably large energies of 100 keV, they are moving at speeds in synch with giant electromagnetic waves that can speed the particles up even more – the same way a well-timed push on a swing can keep it moving higher and higher.

"This paper incorporates the Whistler waves theory previously embraced," said Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "But it provides a new explanation for how the particles get their initial push of energy."

This first mechanism is based on something called time domain structures, which Mozer and his colleagues have identified previously in the belts. They are very short duration pulses of electric field that run parallel to the magnetic fields that thread through the radiation belts. These magnetic field lines guide the movement of all the charged particles in the belts:

The particles move along and gyrate around the lines as if they were tracing out the shape of a spring. During this early phase, the electric pulses push the particles faster forward in the direction parallel to the magnetic fields.

This mechanism can increase the energies somewhat – though not as high as traditionally thought to be needed for the Whistler waves to have any effect. However, Mozer and his team showed, through both data from the Van Allen Probes and from simulations, that Whistlers can indeed affect particles at these lower energies.

Together the one-two punch is a mechanism that can effectively accelerate particles up to the intense speeds, which have for so long mysteriously appeared in the Van Allen belts.

"The Van Allen Probes have been able to monitor this acceleration process better than any other spacecraft because it was designed and placed in a special orbit for that purpose," said Mozer. "The mission has provided the first really strong confirmation of what's happening. This is the first time we can truly explain how the electrons are accelerated up to nearly the speed of light."

Such knowledge helps with the job of understanding the belts well enough to protect nearby spacecraft and astronauts.

The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, built and operates the Van Allen Probes for NASA's Science Mission Directorate. The mission is the second mission in NASA's Living With a Star program, managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland.

For more information about NASA’s Van Allen Probes mission, visit:

www.nasa.gov/vanallenprobes
  

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

Rob Gutro | Eurek Alert!

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>