Van Allen Probes show how to accelerate electrons

Jul 16, 2014 by Karen C. Fox
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. Credit: NASA

(Phys.org) —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? 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 . 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 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.

Explore further: Observations and simulations improve space weather models

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User comments : 8

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George_Rajna
1 / 5 (5) Jul 16, 2014
The accelerating electrons: https://www.acade..._current
Dr_toad
4.2 / 5 (5) Jul 16, 2014
Idiot.
cantdrive85
1.8 / 5 (11) Jul 16, 2014
According to some in these threads astrophysicists are "experts" in plasma physics, reading this article and many others clearly contradicts this claim.

"Students using astrophysical textbooks remain essentially ignorant of even the existence of plasma concepts, despite the fact that some of them have been known for half a century. The conclusion is that astrophysics is too important to be left in the hands of astrophysicists who have gotten their main knowledge from these textbooks. Earthbound and space telescope data must be treated by scientists who are familiar with laboratory and magnetospheric physics and circuit theory, and of course with modern plasma theory." Alfven

One of these days these jokers will catch on to double layers and other ubiquitous plasma phenomena.
Captain Stumpy
3.7 / 5 (9) Jul 16, 2014
According to some in these threads astrophysicists are "experts" in plasma physics, reading this article and many others clearly contradicts this claim
@cd
no, MY claim is that modern astrophysicists are TAUGHT astrophysics, which is proven with this single link: http://www.pppl.gov/

Your claim is that
Students using astrophysical textbooks remain essentially ignorant of even the existence of plasma concepts
which is ALSO proven contradictory with the above link

You have CONTINUED to claim that astrophysicists are "ignorant of plasma physics" and you have YET to produce EVEN ONE PIECE of empirical evidence... One suggestion would be to show ONE SCHOOL that has a FULL astrophysics program that does not include plasma physics in it's curriculum
WHICH YOU HAVE NEVER BEEN ABLE TO DO

I've proven that schools that teach Astrophysics ALSO TEACH PLASMA PHYSICS with the above link and THIS ONE: http://ocw.mit.edu/index.htm

cd=NO EMPIRICAL EVIDENCE=PSEUDOSCIENCE=LIAR
Captain Stumpy
3.7 / 5 (9) Jul 16, 2014
"experts" in plasma physics
@cd
the only thing required to be considered an EXPERT in a field is for the individual to assign the term "expert" to his/her name in conjunction to the field

Thus, even YOU could call yourself an EXPERT in plasma physics

the problem comes when it it time to show your knowledge, to which you will fail miserably because you've never been able to produce reputable links from reputable sites with reputable peer reviewed sources... when you utilise links to KNOWN PSEUDOSCIENCE then you immediately undermine your entire credibility in the eyes of ANYONE who is literate, intelligent, knows science or has ANY ability to do RESEARCH

Thus your claims above, that MIGHT have been valid 40 or so years ago, are considered BLATANT LIES today because the links provided above EMPIRICALLY PROVE that your REPEATED CLAIM is BLATANTLY FALSE and can be considered a REPEATED LIE INTENT ON ESTABLISHING VALIDITY THROUGH REPETITION

it will NOT work
cantdrive85
1.7 / 5 (6) Jul 17, 2014
no, MY claim is that modern astrophysicists are TAUGHT astrophysics,

Yep, couldn't agree more...And hence not one mention of a double layer (basic plasma concept) in the above article. DL's are natural particle accelerators, seems a natural consideration giving they have been found already.

http://journals.a...1.235002

Note they refer to Alfven's papers.

YET to produce EVEN ONE PIECE of empirical evidence.

Except the peer-reviewed paper referred to in a NASA presentation, that which you continually harp about but when presented "proof", claims of conspiracy arise that the papers have been altered since publication. You say something about repeating lies? Right, you've got an M.O.

show ONE SCHOOL that has a FULL astrophysics program that does not include plasma physics in it's curriculum

Why? I've never made that claim they don't, it's all you and your infinite stupidity which still cannot comprehend Alfven's claims.
thermodynamics
5 / 5 (3) Jul 17, 2014
Cantthink: Good to see you posting. I get used to you showing up when there is anything about plasmas. It is good to see that you are keeping to your schedule.

You said:
Except the peer-reviewed paper referred to in a NASA presentation, that which you continually harp about but when presented "proof", claims of conspiracy arise that the papers have been altered since publication. You say something about repeating lies? Right, you've got an M.O.


Can you please give us a link to this? Not that I don't trust you... Oh, sure I don't trust you.

Yep, couldn't agree more...And hence not one mention of a double layer (basic plasma concept) in the above article. DL's are natural particle accelerators, seems a natural consideration giving they have been found already.


You gave a reference to a paper showing the voltage for acceleration. Can you give me luminosity of the electron beam?
cantdrive85
1 / 5 (3) Jul 17, 2014
Cantthink: Good to see you posting. I get used to you showing up when there is anything about plasmas. It is good to see that you are keeping to your schedule.

Being that 99.9999% of the Universe is plasma, I've got plenty of opportunity to keep on schedule.

Can you please give us a link to this? Not that I don't trust you... Oh, sure I don't trust you.

Yep, not a problem. I offered a link to a paper originally published in 'Laser and Particle Beams' by Anthony Peratt. Dr. Peratt has a copy of the paper on his own website, but Cap'n Stupid/CAPS LOCK claimed this here;
http://phys.org/n...rse.html
@cd
and you just magically know that the version you have is legit, un-tampered with and exactly the same as the other?
and we're supposed to take YOUR word on that?


Basically, CONSPIRACY!