Van Allen Probes pinpoint driver of speeding electrons

Jul 25, 2013
An artist's rendering of a mechanism within the Van Allen radiation belts that can accelerate electrons to satellite-killing energies. The mechanism was discovered by a group of scientists using data from NASA's Van Allen Probes (formerly known as the Radiation Belt Storm Probes). Researchers, led by Los Alamos National laboratory space physicist Geoffrey Reeves, believe that electromagnetic waves within the Van Allen belts themselves can accelerate the electrons to near light speed, giving them energy levels that can be lethal to satellites. The research may some day help make space weather forecasting possible and accurate so satellites can be better protected. Credit: Los Alamos National Laboratory

Researchers believe they have solved a lingering mystery about how electrons within Earth's radiation belt can suddenly become energetic enough to kill orbiting satellites. Thanks to data gathered from an intrepid pair of NASA probes roaming the harsh space environment within the Van Allen radiation belts, scientists have identified an internal electron accelerator operating within the belts.

"For years we thought the Van Allen belts were pretty well behaved and changed slowly," said Geoffrey Reeves of Los Alamos National Laboratory's Intelligence and Space Research Division. "With more measurements, however, we realized how quickly and unpredictably the radiation belts change, and now we have real evidence that the changes originate from within the belts themselves."

In a paper released today in Science Express, Reeves and colleagues from the University of New Hampshire, University of Colorado at Boulder, NASA Goddard Flight Center, Aerospace Corporation, University of California-Los Angeles, and University of Iowa, describe a mechanism by which electrons suddenly accelerate to fantastic speeds within the Van Allen belts—a pair of donut shaped zones of charged particles that surround Earth and occupy the inner region of our planet's Magnetosphere.

Traveling at 99 percent the speed of light, the super-fast electrons are among the speediest particles naturally produced by Earth, and have energies so high that they can penetrate and destroy satellite components. The research paves the way for scientists to possibly predict hazardous space weather and allow satellite operators to potentially prepare for the ravages of sudden space storms.

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The radiation belts, named after their discoverer, James Van Allen, are comprised of an outer region of extremely high-energy electrons, with an inner region of energetic protons and electrons. The belts have been studied extensively since the dawn of the Space Age, because the high-energy particles in the outer ring can cripple or disrupt spacecraft. Long-term observation of the belts have hinted that the belts can act as efficient and powerful particle accelerators; recent observations by the Van Allen Probes (formerly known as the Radiation Belt Storm Probes)—a pair of spacecraft launched in August 2012—now seem to confirm this.

On October 9, 2012, while flying through the radiation belts, the Van Allen Probes measured a sudden, nearly thousand-fold increase in the energy of electrons within the outer belt. The rapid increase came on the heels of a period of waning energies the week before. The October 9 event mimicked an observed, but poorly understood event measured in 1997 by another spacecraft. Ever since the 1997 event, scientists have pondered whether the increase in electron energy was the result of forces outside of the belts, a mechanism known as "radial acceleration," or from forces within the belts, known as "local acceleration." Data from the Van Allen Probes seems to put this question to rest.

Because the twin Van Allen Probes follow each other and cut through the belts at different times, researchers were able to see that the October 9 increase originated from within the heart of the belts, indicative of local acceleration. The data also showed that higher electron fluxes did not move from a region outside of the belts slowly toward our planet, a detail corroborated by other geosynchronous satellites located outside of the belts.

"In the October 9, 2012, event, all of the acceleration took place in about 12 hours," said Reeves, a space physicist and principal author of the Science paper. "With previous measurement, a satellite might have only been able to fly through such an event once and not get a chance to witness the changes actually happening."

The researchers are now trying to understand exactly how the acceleration took place. Right now, the team believes that electromagnetic radio waves somehow excite the electrons into a higher-energy state, much like a microwave oven excites and heats water molecules. Members of the team are looking hard at waves known as "Chorus Waves" that are often observed in the region of the belts where the local acceleration was strongest. Chorus Waves are a type of electromagnetic radio wave with frequencies within the range of human hearing. Chorus Waves provide a haunting cacophony like a flock of extraterrestrial birds.

"We don't know whether it is Chorus Waves or some other type of electromagnetic wave that's behind the electron acceleration we are seeing," said Reeves, "but the Van Allen Probes are also equipped with instruments that should help us figure that out as well. Each of these discoveries take us a step closer to the goal of forecasting these extreme space weather events and making space safer for satellites."

Explore further: NASA to make announcement on US human spaceflights

More information: "The Savage Radiation of the Van Allen Belts Is Homegrown", Science vol 341 26 July 2013

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User comments : 11

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El_Nose
3 / 5 (2) Jul 25, 2013
Why do we still have the radiation belts?

We currently know that we could discharge them, so are we keeping them around because we are not sure if they serve other purposes... which I get, don;t change something that might be saving your planet if you don;t know what it does.. or are we saving them to mine antimatter?

I just don;t get why we haven't at least gotten rid of the low orbit one
cantdrive85
1 / 5 (5) Jul 25, 2013
The researchers are now trying to understand exactly how the acceleration took place. Right now, the team believes that electromagnetic radio waves somehow excite the electrons into a higher-energy state, much like a microwave oven excites and heats water molecules.

Well, if they had any real understanding of plasma physics whatsoever, they may realize the most likely source of the particle acceleration is a naturally occurring plasma formation, the plasma double layer (DL). DL's occur naturally between two adjacent plasmas with differing properties, such as the inner and outer ring. Yet, here they are forcing magnetofluid dynamics where, as has been stated repeatedly, they don't belong.

To reiterate, DL's can form naturally between inhomogeneous plasmas (supported by volumes of lab data), DL's are natural particle accelerators (once again, supported by VOLUMES of lab data). Why wouldn't this remarkably simple and lab supported explanation be considered? I'd say ignorance.
Protoplasmix
1 / 5 (3) Jul 25, 2013
I just don;t get why we haven't at least gotten rid of the low orbit one

What if it's acting as a plasma window or plasma bubble of sorts?

Wouldn't the belts also fill right back up with protons anyway? And wouldn't those protons (and alpha particles) come from the interaction of our air with cosmic rays and solar wind? So wouldn't that zap our atmosphere that much faster?
cantdrive85
1 / 5 (5) Jul 25, 2013
Why do we still have the radiation belts?

We currently know that we could discharge them, so are we keeping them around because we are not sure if they serve other purposes...

Oh, really? I don't have the language capacity to explain how ridiculous your post is without resorting to vulgarities, so I'll just leave it at that.

I just don;t get why we haven't at least gotten rid of the low orbit one

LOL, wait, is this humor?
Protoplasmix
1 / 5 (2) Jul 25, 2013
Why do we still have the radiation belts?

We currently know that we could discharge them, so are we keeping them around because we are not sure if they serve other purposes...

Oh, really? I don't have the language capacity to explain how ridiculous your post is without resorting to vulgarities, so I'll just leave it at that.

I just don;t get why we haven't at least gotten rid of the low orbit one

LOL, wait, is this humor?

See HiVOLT. *cough *
cantdrive85
1 / 5 (4) Jul 25, 2013
Why do we still have the radiation belts?

We currently know that we could discharge them, so are we keeping them around because we are not sure if they serve other purposes...

Oh, really? I don't have the language capacity to explain how ridiculous your post is without resorting to vulgarities, so I'll just leave it at that.

I just don;t get why we haven't at least gotten rid of the low orbit one

LOL, wait, is this humor?

See http://en.wikiped.../HiVOLT. *cough *

I think enough has been learned about the belts, any notion such as the above is complete nonsense. You may as well drain the oceans.
Protoplasmix
2.3 / 5 (3) Jul 26, 2013
Not sure, but I think the danger of a little knowledge is transformed by a diminished vocabulary into comedy.

Good question about the antimatter in the belts, El_Nose, it's on my list of things to learn more about :)

__________________
"No, it'll be really funny, watch" - Prometheus
cantdrive85
1 / 5 (4) Jul 27, 2013
This is along the lines of what I mean;
http://www.nasa.g...P_Y2TgbI

The article shows how the Sun can add to, and take away from the belts. As said, you may as well drain the oceans,
El_Nose
not rated yet Jul 29, 2013
@cantdriver85

FYI -- Due to the nature of your responce I will explain. NASA has long thought that getting rid of the radiation belts might be the best way of dealing with them.

As to how -- all that is needed is 5x wires that are around 100 km long. Please google "High Voltage Orbiting Long Tether (HiVOLT)" we have know how to get rid of the belts for a long long time. its just a matter of discharging the field.

--- as far as the sun adding to the belts -- valid point -- but

as the wires remain in place they act as a functional ground -- meaning that the fields are constantly being discharged, much like a sink with the drain open. It is not like draining the ocean, because on Earth there is nowhere for the water to go,,, however it is relatively simple to drain a charged feild as you are changing the route the energy takes.

thanks @Protoplasmix
GSwift7
not rated yet Jul 30, 2013
I would suggest you make REALLY sure that the VA Belt isn't doing some important job in regard to our health and safety before you think about removing it.

If you could be sure that the belt would re-build itself, then it's worth a try. Maybe you could even just deploy the grounding wires when you see one of the above mentioned electron storms starting up, or when a spacecraft leaving earth orbit is passing through?

I still say caution is wise though. Until we get a better understanding of the VA Belt, it's just too unpredictable to mess with. As with forest fires, you could get a massive whiplash effect by holding it back. Who knows if there's some kind of stored up potential that the belt helps release. Is there a similar belt around any other planet that we could test this on? Experimenting on our own planet is like nibbling on berries and mushrooms in the woods to see if they are poisonous.
cantdrive85
1 / 5 (4) Jul 30, 2013
I would suggest you make REALLY sure that the VA Belt isn't doing some important job in regard to our health and safety before you think about removing it.


To be sure, the belts are a predictable manifestation of a charged sphere within a plasma environment. Birkeland observed them with his Terella experiments, and Alfven described them prior to Van Allen as well. The belts are an integral part of the Earth's EM field. Also, these belts are within the Earth's EM field, to truly "ground" the circuit, the tethers would need to extend beyond the Earth's EM field.