Starship Asterisk*

[i]Graphic depicting the twin Van Allen Probes in orbit within Earth's magnetic field. [b](Credit: JHU/APL)[/b][/i]

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This high-cadence sampling data, taken by the Electric and Magnetic Field Instrument
Suite and Integrated Science (EMFISIS) instruments on NASA's Van Allen Probes right
after launch, reveals a strong correlation between chorus waves (the bird-like sounds
recorded by EMFISIS) and disturbance storm time (DST), a value used to measure
geomagnetic activity during magnetic storms. A drop in DST (top) can be seen to
correlate with an increase in chorus activity (more red, orange, and yellow) in the
bottom plot. This correlation may be central to the association of strong particle
acceleration with some magnetic storms; scientists are working now to learn more
about the exact processes at work. (Credit: University of Iowa/NASA)

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Just 96 days since their launch, NASA’s twin Van Allen Probes have already provided new insights into the structure and behavior of the radiation belts that surround Earth, giving scientists a clearer understanding about the fundamental physical properties of these regions more than half a century after their discovery.

In a press conference on Tuesday, Dec. 4 at the American Geophysical Union’s 2012 Fall Meeting in San Francisco, members of the Van Allen Probes science team discussed current findings made in unlocking the mysteries of the radiation belts. These two donut-shaped regions of high-energy and hazardous particles – named for their discoverer and the mission’s namesake, American physicist James Van Allen of the University of Iowa – are created by our planet’s magnetosphere, and can harm space technologies such as satellites, as well as affect human space travel.

Throughout the brief early life of the two-year mission, energetic events and ejections of plasma from the sun caused dramatic changes in the radiation belts that, for the first time, were observed by twin spacecraft within the belts. “The sun has been a driver of these systems more than we had any right to expect,” says Daniel Baker, Principal Investigator, Van Allen Probes Relativistic Electron Proton Telescope (REPT, which is part of the Energetic Particle, Composition, and Thermal Plasma Suite, or ECT), from the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder. “We’re seeing brand new features we hadn’t expected.”

The twin probes, built and managed for NASA by the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., contain identical sets of five instrument suites. These suites have confirmed previous hypotheses about the belts’ behavior, while also revealing that the belts are a far more dynamic and changing environment than previously thought. “We expected to see a fairly placid radiation belt system,” Baker says. “Instead, we see that the belts have been extraordinarily active and dynamic during the first few weeks. We’re looking in the right places at the right times.”

Our planet’s magnetosphere captures particles from the billions of tons of plasma ejected by the sun and from other sources; fields and waves of electricity and magnetism control and guide the charged particles within the belts, with the particles “surfing” on the waves, losing or gaining large amounts of energy along the way as they enter and leave the region. Measurements made by instruments like the Electric Fields and Waves Suite (EFW) and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) are helping scientists understand how those fields and waves affect the particles. “The electric field and magnetic field measurements on the Van Allen Probes are the best ever made in the radiation belts,” says the University of Iowa’s Craig Kletzing, Principal Investigator for EMFISIS. “For the first time, we’ve been able to see how long intense low frequency electric fields and waves at the edge of the radiation belts can last – sometimes for over five hours during geomagnetic storms. Before, it was like we could see a car zoom past, but not see anything about the details. Now, we can see what color the upholstery is.”

The inner belt, where many satellites must operate, is home to the most hazardous and energized particles, mostly protons. “A staggering number of the spacecraft we rely upon daily have to spend a part of their orbit in the harshest area of Earth’s radiation environment,” says Joseph Mazur of the Aerospace Corporation, Principal Investigator of the probes’ Relativistic Proton Spectrometer (RPS). The Van Allen Probes are providing researchers with detailed views of how the populations of those particles vary with altitude, which should help engineers more effectively protect satellites. “This is the first time we’ve been able to measure the high energy particles in the heart of the radiation belts,” Mazur said. “We’re able to measure at the one billion electron volt level; particles at that energy are virtually impossible to shield against. They will easily penetrate half-inch thick aluminum plate.” Particles at that energy level are known to cause a range of damages to spacecraft, from physical degradation to instrument malfunctions and false readings.

“NASA built these spacecraft to be super tough, and thank goodness we did,” says APL’s Nicky Fox, Van Allen Probes deputy project scientist. “The instruments are seeing the exact sorts of damaging effects we designed the spacecraft to survive.”

bystander wrote:Van Allen Probes Reveal New Dynamics of Earth's Radiation Belts

NASA | JHU-APL | Van Allen Probes (RBSP) | 2012 Dec 05

“The electric field and magnetic field measurements on the Van Allen Probes are the best ever made in the radiation belts,” says the University of Iowa’s Craig Kletzing, Principal Investigator for EMFISIS. “For the first time, we’ve been able to see how long intense low frequency electric fields and waves at the edge of the radiation belts can last – sometimes for over five hours during geomagnetic storms.

Before, it was like we could see a car zoom past, but not see anything about the details. Now, we can see what color the upholstery is.”

Click to play embedded YouTube video.

Click to play embedded YouTube video.

[i]Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958. In 2012, observations from the Van Allen Probes showed that a third belt can sometimes appear. The radiation is shown here in yellow, with green representing the spaces between the belts. [b](Credit: NASA/GSFC/Van Allen Probes)[/b][/i]

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On Aug. 31, 2012, a giant prominence on the sun erupted, sending out particles and a
shock wave that traveled near Earth. This event may have been one of the causes of a
third radiation belt that appeared around Earth a few days later, a phenomenon that
was observed for the very first time by the newly-launched Van Allen Probes. This
image of the prominence before it erupted was captured by NASA's Solar Dynamics
Observatory (SDO). (Credit: NASA/GSFC/SDO/AIA)

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After most NASA science spacecraft launches, researchers wait patiently for months as instruments on board are turned on one at a time, slowly ramped up to full power, and tested to make sure they work at full capacity. It's a rite of passage for any new satellite in space, and such a schedule was in place for the Van Allen Probes when they launched on Aug. 30, 2012, to study two giant belts of radiation that surround Earth.

But a group of scientists on the mission made a case for changing the plan. They asked that the Relativistic Electron Proton Telescope (REPT) be turned on early – just three days after launch -- in order that its observations would overlap with another mission called SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), that was soon going to de-orbit and re-enter Earth's atmosphere.

It was a lucky decision. Shortly before REPT turned on, solar activity on the sun had sent energy toward Earth that caused the radiation belts to swell. The REPT instrument worked well from the moment it was turned on Sep. 1. It made observations of these new particles trapped in the belts, recording their high energies, and the belts' increased size.

Then something happened no one had ever seen before: the particles settled into a new configuration, showing an extra, third belt extending out into space. Within mere days of launch, the Van Allen Probes showed scientists something that would require rewriting textbooks.

"By the fifth day REPT was on, we could plot out our observations and watch the formation of a third radiation belt," says Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA's Goddard Space Flight Center in Greenbelt, Md. and a coauthor of a paper on these results. "We started wondering if there was something wrong with our instruments. We checked everything, but there was nothing wrong with them. The third belt persisted beautifully, day after day, week after week, for four weeks."

The scientists published their results in a paper in the journal Science on Feb. 28, 2013. Incorporating this new configuration into their models of the radiation belts offers scientists new clues to what causes the changing shapes of the belts – a region that can sometimes swell dramatically in response to incoming energy from the sun, impacting satellites and spacecraft or pose potential threats to manned space flight.

The radiation belts, or Van Allen belts, were discovered with the very first launches of satellites in 1958 by James Van Allen. Subsequent missions have observed parts of the belts – including SAMPEX, which observed the belts from below – but what causes such dynamic variation in the belts has remained something of a mystery. Indeed, seemingly similar storms from the sun have at times caused completely different effects in the belts, or have sometimes led to no change at all.

The Van Allen Probes consist of two identical spacecraft with a mission to map out this region with exquisite detail, cataloguing a wide range of energies and particles, and tracking the zoo of magnetic waves that pulse through the area, sometimes kicking particles up to such frenzied speeds that they escape the belts altogether.

"We've had a long run of data from missions like SAMPEX," says Daniel Baker, who is the principal investigator for REPT at the University of Colorado in Boulder and first author on the Science paper. "But we've never been in the very throat of the accelerator operating a few hundred miles above our head, speeding these particles up to incredible velocities."

In its first six months in orbit, the instruments on the Van Allen Probes have worked exceptionally well and scientists are excited about a flood of observations coming in with unprecedented clarity. This is the first time scientists have been able to gather such a complete set of data about the belts, with the added bonus of watching from two separate spacecraft that can better show how events sweep across the area.

Spotting something new in space such as the third radiation belt has more implications than the simple knowledge that a third belt is possible. In a region of space that remains so mysterious, any observations that link certain causes to certain effects adds another piece of information to the puzzle.

Baker likes to compare the radiation belts to the particle storage rings in a particle physics accelerator. In accelerators, magnetic fields are used to hold the particles orbiting in a circle, while energy waves are used to buffet the particles up to ever faster speeds. In such accelerators, everything must be carefully tuned to the size and shape of that ring, and the characteristics of those particles. The Van Allen Belts depend on similar fine-tuning. Given that scientists see the rings only in certain places and at certain times, they can narrow down just which particles and waves must be causing that geometry. Every new set of observations helps narrow the field even further.

"We can offer these new observations to the theorists who model what's going on in the belts," says Kanekal. "Nature presents us with this event – it's there, it's a fact, you can't argue with it -- and now we have to explain why it's the case. Why did the third belt persist for four weeks? Why does it change? All of this information teaches us more about space."

Scientists already have theories about just what kind of waves sweep out particles in the "slot" region between the first two belts. Now they must devise models to find which waves have the right characteristics to sweep out particles in the new slot region as well. Another tantalizing observation to explore lies in tracking the causes of the slot region back even further: on Aug. 31, 2012, a long filament of solar material that had been hovering in the sun's atmosphere erupted out into space. Baker says that this might have caused the shock wave that led to the formation of the third ring a few days later. In addition, the new belt was virtually annihilated four weeks after it appeared by another powerful interplanetary shock wave from the sun. Being able to watch such an event in action provides even more material for theories about the Van Allen belts.

Despite the 55 years since the radiation belts were first discovered, there is much left to investigate and explain, and within just a few days of launch the Van Allen Probes showed that the belts are still capable of surprises.

"I consider ourselves very fortunate," says Baker. "By turning on our instruments when we did, taking great pride in our engineers and having confidence that the instruments would work immediately and having the cooperation of the sun to drive the system the way it did – it was an extraordinary opportunity. It validates the importance of this mission and how important it is to revisit the Van Allen Belts with new eyes."

• Science (online 2013 Feb 28) DOI: 10.1126/science.1233518

Los Alamos 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.

[i]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. [b](Image credit: Los Alamos National Laboratory)[/b][/i]

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Research team solves decades-old mystery that threatens satellites

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.

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.”

• Science (online 25 Jul 2013) DOI: 10.1126/science.1237743

bystander wrote:
Van Allen Probes Pinpoint Driver of Speeding Electrons
Los Alamos National Laboratory | 2013 Jul 25

“In a paper released today in Science Express, Reeves and colleagues ... describe a mechanism by which electrons suddenly accelerate to fantastic speeds within the Van Allen belts. 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.

Click to play embedded YouTube video.

By taking into consideration how the fastest particles in the radiation
belts move, and how they behave differently from less energetic particles,
researches have created simulations of the radiation belts that better
match what is actually observed. (Image Credit: Y. Shprits)

[i]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. [b](Image Credit: NASA/Goddard Space Flight Center)[/b][/i]

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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.

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.

• Nature Physics (online 22 Sept 2013) DOI: 10.1038/nphys2760

• Geophysical Research Letters 40(14) 3507 (28 July 2013) DOI: 10.1002/grl.50627

Van Allen Probes Shed Light on Decades-old Mystery

New research using data from NASA's Van Allen Probes mission helps resolve decades of scientific uncertainty over the origin of ultra-relativistic electrons in Earth's near space environment, and is likely to influence our understanding of planetary magnetospheres throughout the universe.

Understanding the processes that control the formation and ultimate loss of such relativistic electrons is a primary science objective of the Van Allen Probes and has important practical applications, because of the enormous amounts of radiation trapped within the two Van Allen radiation belts. The belts, consisting of high-energy electrons and protons discovered above Earth's upper atmosphere in 1958 by James Van Allen, can pose a significant hazard to satellites and spacecraft, as well to astronauts performing activities outside a spacecraft.

Such electrons in the Earth's outer radiation belt can exhibit pronounced increases in intensity, in response to activity on the sun, and changes in the solar wind — but the dominant physical mechanisms responsible for such radiation belt electron acceleration has remained unresolved for decades.

Two primary candidates for electron acceleration exist, one external and one internal. From outside the belts, a theoretical process known as inward radial diffusive transport has been developed. From within the belts, scientists hypothesize that the electrons are undergoing strong local acceleration from very low frequency plasma waves. Controversies also exist as to the very nature of the wave acceleration: Is it stochastic – that is, a linear and diffusive process – or is it non-linear and coherent?

In research published Dec. 19, 2013, in Nature*, lead author Richard Thorne and colleagues report on high-resolution measurements, made by the Van Allen Probes, which suggest that local acceleration is at work. The team observed high-energy electrons during a geomagnetic storm of Oct. 9, 2012, which they analyzed together with a data-driven global wave model. Their analysis reveals that linear, stochastic scattering by intense, natural very low-frequency radio waves -- known as chorus waves -- in Earth's upper atmosphere can account for the observed relativistic electron build-up.

http://www.planetary.org/blogs/emily-lakdawalla/2014/01100912-finally-some-high-quality-change3.html wrote:

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Finally, some high-quality photos from Chang'e 3!
Posted by Emily Lakdawalla
2014/01/10 11:37 CST

The extreme ultraviolet camera on Chang'e 3 studies the plasma environment around Earth at a wavelength of 63 nanometers.

This image was taken shortly after Chang'e 3's landing, on December 16, 2013.

http://www.planetary.org/blogs/emily-lakdawalla/2014/01141430-updates-on-change-3.html wrote:

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Updates on Chang'e 3: Rover and lander both awake
Posted by Emily Lakdawalla, 2014/01/14 05:01 CST

Here's an ultraviolet view of Earth. I posted something similar on Friday, but I learned from the Chinese Academy of Sciences website that what I posted (on Friday) was actually a computer simulation of what Earth's plasmasphere should look like from the lander's extreme ultraviolet camera.

This image is the actual data from the camera.

The extreme ultraviolet camera on Chang'e 3 studies the plasma environment around Earth at a wavelength of 63 nanometers taken shortly after Chang'e 3's landing, on December 16, 2013.

New NASA Van Allen Probes Observations Helping To Improve Space Weather Models
Excerpt from news release of
March 7, 2014
Using data from NASA's Van Allen Probes, researchers have tested and improved a model to help forecast what's happening in the radiation environment of near-Earth space -- a place seething with fast-moving particles and a space weather system that varies in response to incoming energy and particles from the sun.

Click to view full size image

When events in the two giant doughnuts of radiation around Earth – called the Van Allen radiation belts -- cause the belts to swell and electrons to accelerate to 99 percent the speed of light, nearby satellites can feel the effects. Scientists ultimately want to be able to predict these changes, which requires understanding of what causes them.
Now, two sets of related research published in the Geophysical Research Letters improve on these goals. By combining new data from the Van Allen Probes with a high-powered computer model, the new research provides a robust way to simulate events in the Van Allen belts.

[url=http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4241][b][i]Radiation Belts & Plasmapause[/i][/b][/url] - [b][i]Credit: NASA/GSFC/SVS/Tom Bridgman (GST)[/i][/b] [i]Visualization of the radiation belts with confined charged particles (blue & yellow) and plasmapause boundary (blue-green surface)[/i]

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Two donuts of seething radiation that surround Earth, called the Van Allen radiation belts, have been found to contain a nearly impenetrable barrier that prevents the fastest, most energetic electrons from reaching Earth.

The Van Allen belts are a collection of charged particles, gathered in place by Earth’s magnetic field. They can wax and wane in response to incoming energy from the sun, sometimes swelling up enough to expose satellites in low-Earth orbit to damaging radiation. The discovery of the drain that acts as a barrier within the belts was made using NASA's Van Allen Probes, launched in August 2012 to study the region. A paper on these results appeared in the Nov. 27, 2014, issue of Nature magazine.

“This barrier for the ultra-fast electrons is a remarkable feature of the belts," said Dan Baker, a space scientist at the University of Colorado in Boulder and first author of the paper. "We're able to study it for the first time, because we never had such accurate measurements of these high-energy electrons before."

Understanding what gives the radiation belts their shape and what can affect the way they swell or shrink helps scientists predict the onset of those changes. Such predictions can help scientists protect satellites in the area from the radiation. ...

• Nature 515(7528) 531 (27 Nov 2014) DOI: 10.1038/nature13956

Solar storm found to produce 'ultrarelativistic, killer electrons' in 60 seconds.

On Oct. 8, 2013, an explosion on the sun's surface sent a supersonic blast wave of solar wind out into space. This shockwave tore past Mercury and Venus, blitzing by the moon before streaming toward Earth. The shockwave struck a massive blow to the Earth's magnetic field, setting off a magnetized sound pulse around the planet.

NASA's Van Allen Probes, twin spacecraft orbiting within the radiation belts deep inside the Earth's magnetic field, captured the effects of the solar shockwave just before and after it struck.

Now scientists at MIT's Haystack Observatory, the University of Colorado, and elsewhere have analyzed the probes' data, and observed a sudden and dramatic effect in the shockwave's aftermath: The resulting magnetosonic pulse, lasting just 60 seconds, reverberated through the Earth's radiation belts, accelerating certain particles to ultrahigh energies.

"These are very lightweight particles, but they are ultrarelativistic, killer electrons -- electrons that can go right through a satellite," says John Foster, associate director of MIT's Haystack Observatory. "These particles are accelerated, and their number goes up by a factor of 10, in just one minute. We were able to see this entire process taking place, and it's exciting: We see something that, in terms of the radiation belt, is really quick."

The findings represent the first time the effects of a solar shockwave on Earth's radiation belts have been observed in detail from beginning to end. Foster and his colleagues have published their results in the Journal of Geophysical Research. ...

• Journal of Geophysical Research DOI: 10.1002/2014JA020642

Understanding the shape and size of the belts, which shrink and swell in response to magnetic storms coming from the sun, is crucial for protecting our technology in space.

Click to play embedded YouTube video.

The shape of the two electron swarms 600 miles to more than 25,000 miles from the Earth’s surface, known as the Van Allen Belts, could be quite different than has been believed for decades, according to a new study of data from NASA’s Van Allen Probes that was released Friday in the Journal of Geophysical Research.

“The shape of the belts is actually quite different depending on what type of electron you’re looking at,” said Geoff Reeves of Los Alamos National Laboratory’s Intelligence and Space Research Division and lead author on the study. “Electrons at different energy levels are distributed differently in these regions.”

Understanding the shape and size of the belts, which shrink and swell in response to magnetic storms coming from the sun, is crucial for protecting our technology in space. The harsh radiation isn't good for satellite's health, so scientists want to know just which orbits could be jeopardized in different situations. ...

• Journal of Geophysical Research 121(1):397 (2016 Jan) DOI: 10.1002/2015JA021569

[img3="During periods when there are no geomagnetic storms affecting the area around Earth (left image), high-energy protons (with energy of hundreds of thousands of electronvolts, or keV; shown here in orange) carry a substantial electrical current that encircles the planet, also known as the ring current. During periods when geomagnetic storms affect Earth (right), new low-energy protons (with energy of tens of thousands of electronvolts, or keV; shown here in magenta) enter the near-Earth region, enhancing the pre-existing ring current. (Credit: JHU-APL)"]http://www.nasa.gov/sites/default/files ... raphic.jpg[/img3][hr][/hr]

New findings based on a year's worth of observations from NASA’s Van Allen Probes have revealed that the ring current – an electrical current carried by energetic ions that encircles our planet – behaves in a much different way than previously understood.

The ring current has long been thought to wax and wane over time, but the new observations show that this is true of only some of the particles, while other particles are present consistently. Using data gathered by the Radiation Belt Storm Probes Ion Composition Experiment, or RBSPICE, on one of the Van Allen Probes, researchers have determined that the high-energy protons in the ring current change in a completely different way from the current’s low-energy protons. Such information can help adjust our understanding and models of the ring current – which is a key part of the space environment around Earth that can affect our satellites. ...

• Geophysical Research Letters (online 19 May 2016) DOI: 10.1002/2016GL068013