Artist’s impression of an aurora and the surrounding radiation belt of the ultracool dwarf LSR J1835+3259. Credit: Chuck Carter/Melodie Kao/Heising-Simons Foundation)
In 1958, the first satellites launched by the United States (Explorer 1and 3) detected a massive radiation belt around planet Earth. This confirmed something that many scientists suspected before the Space Age began: that energetic particles emanating from the Sun (solar wind) were captured and held around the planet by Earth’s magnetosphere. This region was named the Van Allen Belt in honor of University of Iowa professor James Van Allen who led the research effort. As robotic missions explored more of the Solar System, scientists discovered similar radiation belts around Jupiter, Saturn, Uranus, and Neptune.
Given the boom in extrasolar planet research, scientists have eagerly awaited the day when a Van Allen Belt would be discovered around an exoplanet. Thanks to a team of astronomers led by the University of California, Santa Cruz (UCSC) and the National Radio Astronomy Observatory (NRAO), that day may have arrived! Using the global High Sensitivity Array (HSA), the team obtained images of persistent, intense radio emissions from an ultracool dwarf star. These revealed the presence of a cloud of high-energy particles forming a massive radiation belt similar to what scientists have observed around Jupiter.
An artist’s rendering of the Van Allen radiation belts surrounding Earth. The purple, concentric shells represent the inner and outer belts. They completely encircle Earth, but have been cut away in this image to show detail. Image Credit: NASA’s Conceptual Image Lab/Walt Feimer
Earth’s fleet of satellites is in a vulnerable position. When solar activity increases, high-energy particles are directed toward Earth. Our large fleet is in the direct path of all that energy, which can damage them or render them inoperable. But now we have another tool to help us protect our satellites.
Artist's depiction with cutaway section of the two giant donuts of radiation, called the Van Allen Belts, that surround Earth. Credit: NASA
Human beings have known for quite some time that our behavior has a significant influence on our planet. In fact, during the 20th century, humanity’s impact on the natural environment and climate has become so profound that some geologists began to refer to the modern era as the “Anthropocene”. In this age, human agency is the most deterministic force on the planet.
But according to a comprehensive new study by an Anglo-American team of researchers, human beings might be shaping the near-space environment as well. According to the study, radio communications, EM radiation from nuclear testing and other human actions have led to the creation of a barrier around Earth that is shielding it against high-energy space radiation.
The study, which was published in the journal Space Science Reviews under the title “Anthropogenic Space Weather“, was conducted by a team of scientists from the US and Imperial College, London. Led by Dr. Tamas Gombosi, a professor at the University of Michigan and the director at the Center for Space Modelling, the team reviewed the impact anthropogenic processes have on Earth’s near-space environment.
These processes include VLF and radio-frequency (RF) radio communications, which began in earnest during the 19th century and grew considerably during the 20th century. Things became more intense during the 1960s when the United States and the Soviet Union began conducting high-altitude nuclear tests, which resulted in massive electromagnetic pulses (EMP) in Earth’s atmosphere.
To top it off, the creation of large-scale power grids has also had an impact on the near-space environment. As they state in their study:
“The permanent existence, and growth, of power grids and of VLF transmitters around the globe means that it is unlikely that Earth’s present-day space environment is entirely “natural” – that is, that the environment today is the environment that existed at the onset of the 19th century. This can be concluded even though there continue to exist major uncertainties as to the nature of the physical processes that operate under the influence of both the natural environment and the anthropogenically-produced waves.”
The existence of radiation belts (or “toroids”) around Earth has been a well-known fact since the late 1950s. These belts were found to be the result of charged particles coming from the Sun (i.e. “solar wind”) that were captured by and held around Earth by it’s magnetic field. They were named Van Allen Radiation Belts after their discover, the American space scientist James Van Allen.
The twin Radiation Belt Storm Probes, later renamed the Van Allen Probes. Credit: NASA/JHUAPL
The extent of these belts, their energy distribution and particle makeup has been the subject of multiple space missions since then. Similarly, studies began to be mounted around the same time to discover how human-generated charged particles, which would interact with Earth’s magnetic fields once they reached near-space, could contribute to artificial radiation belts.
However, it has been with the deployment of orbital missions like the Van Allen Probes (formerly the Radiation Belt Storm Probes) that scientists have been truly able to study these belts. In addition to the aforementioned Van Allen Belts, they have also taken note of the VLF bubble that radio transmissions have surrounded Earth with. As Phil Erickson, the assistant director at the MIT Haystack Observatory, said in a NASA press release:
“A number of experiments and observations have figured out that, under the right conditions, radio communications signals in the VLF frequency range can in fact affect the properties of the high-energy radiation environment around the Earth.”
One thing that the probes have noticed was the interesting way that the outward extent of the VLF bubble corresponds almost exactly to the inner and outer Van Allen radiation belts. What’s more, comparisons between the modern extent of the radiations belts from the Van Allen Probe data shows that the inner boundary is much farther away than it appeared to be during the 1960s (when VLF transmissions were lower).
Two giant belts of radiation surround Earth. The inner belt is dominated by protons and the outer one by electrons. Credit: NASA
What this could mean is that the VLF bubble we humans have been creating for over a century and half has been removing excess radiation from the near-Earth environment. This could be good news for us, since the effects of charged particles on electronics and human health is well-documented. And during periods of intense space weather – aka. solar flares – the effects can be downright devastating.
Given the opportunity for further study, we may find ways to predictably and reliably use VLF transmissions to make the near-Earth environment more human and electronics-friendly. And with companies like SpaceX planning on bringing internet access to the world through broadband internet-providing satellites, and even larger plans for the commercialization of Near-Earth Orbit, anything that can mitigate the risk posed by radiation is welcome.
And be sure to check this video that illustrates the Van Allen Probes findings, courtesy of NASA:
This is an illustration to explain the dynamics of the ultra-relativistic third Van Allen radiation belt. Credit: Andy Kale
The dynamic relationship between Earth and the Sun two sides. The warmth from the Sun makes life on Earth possible, but the rest of the Sun’s intense energy pummels the Earth, and could destroy all life, given the chance. But thanks to our magnetosphere, we are safe.
The magnetosphere is our protective shield. It’s created by the rotation of the molten outer core of the Earth, composed largely of iron and nickel. It absorbs and deflects plasma from the solar wind. The interactions between the magnetosphere and the solar wind are what create the beautiful auroras at Earth’s poles.
Visualization of the solar wind encountering Earth’s magnetic “defenses” known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet’s nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL
In the inner regions of Earth’s magnetosphere are the Van Allen belts, named after their discoverer James Van Allen. They consist of charged particles, mostly from the Sun, and are held in place by the magnetosphere. Usually, there are two such belts.
The Van Allen radiation belts surrounding Earth. Image: NASA
But the output from the Sun is not stable. There are periods of intense energy output from the Sun, and when that happens, a third, transient belt can be created. Up until now, the nature of this third belt has been a puzzle. New research from the University of Alberta has shown how this phenomena can happen.
Researchers have shown how a so-called “space tsunami” can create this third belt. Intense ultra-low frequency plasma waves can transport the outer part of the radiation belt into interplanetary space, and create the third, transient belt.
The lead author for this study is physics professor Ian Mann from the University of Alberta, and former Canada Research Chair in Space Physics. “Remarkably, we observed huge plasma waves,” said Mann. “Rather like a space tsunami, they slosh the radiation belts around and very rapidly wash away the outer part of the belt, explaining the structure of the enigmatic third radiation belt.”
This new research also sheds light on how these “tsunamis” help reduce the threat of radiation to satellites during other space storms. “Space radiation poses a threat to the operation of the satellite infrastructure upon which our twenty-first century technological society relies,” adds Mann. “Understanding how such radiation is energized and lost is one of the biggest challenges for space research.”
It’s not just satellites that are at risk of radiation though. When solar wind is most active, it can create extremely energetic space storms. They in turn create intense radiation in the Van Allen belts, which drive electrical currents that could damage our power grids here on Earth. These types of storms have the potential to cause trillions of dollars worth of damage.
A better understanding of this space radiation, and an ability to forecast it, are turning out to be very important to our satellite operations, and to our exploration of space.
The Van Allen belts were discovered in 1958, and classified into an inner and an outer belt.
The Van Allen Belts around Earth. The inner red belt is mostly protons, and the outer blue belt is mostly electrons. Image Credit: NASA
In 2013, probes reported a third belt which had never before been seen. It lasted a few weeks, then vanished, and its cause was not known. Thanks to Mann and his team, we now know what was behind that third belt.
“We have discovered a very elegant explanation for the dynamics of the third belt,” says Mann. “Our results show a remarkable simplicity in belt response once the dominant processes are accurately specified.”
An understanding of the radiation in and around Earth and the Van Allen belts is of growing importance to us, as we expand our presence in space. Our technological society relies increasingly on satellite communications, and on GPS satellites. Radiation in the form of high-energy electrons can wreak havoc on satellites. In fact, this type of radiation is sometimes referred to as a satellite killer. Satellites require robust design to be protected from them.
Organizations like the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the International Living with a Star (ILWS) Program are attempts to address the threat that radiation poses to our system of satellites.
When humans finally travel into space, where will we live? Will we ever be able to colonize gas giants like Jupiter?
NASA and Elon Musk have plans to get your ass to Mars.
It’s not impossible to imagine humans living and working on the Red Planet. Maybe they’ll be crusty asteroid miners making their fortune digging precious minerals out of the inexhaustible supply of space rocks. Pray they don’t dig too deeply. We should go ask Kuato, that creepy little guy knows everything! Except he’s always trying to get you to touch his funny little hands. Pass.
Venus looks like it’s a pretty great place to live, if we stick to the clouds in floating sky cities, plying the jet streams in our steampunk dirigibles. It’ll be fun, but first, does anyone know how to attach a cog to a top hat? Venus, here we come!
We should stay away from the surface, though, that place’ll kill you dead. We’re guessing a crispy shell holding in a gooey center, at least for the first few moments. Once we sort the living in space deal, is there anywhere we won’t be able to go?
We could create underwater cities on Europa or Ganymede, in the vast oceans with the exotic hopefully unarmed, peaceful, vegetarian Jovian whales.Like Jupiter? Could we live there?
Jupiter is the most massive planet in the Solar System. It has a diameter of almost 140,000 kilometers and it’s made mostly of hydrogen and helium; the same materials of the Sun. It has more than 317 times the mass of the Earth, providing its enormous gravity.
If you could stand on the cloud tops of Jupiter, you would experience 2.5 times the gravity that you experience on Earth. Then you’d fall to your death, because it’s a gas planet, made of hydrogen, the lightest element in the Universe. You can’t stand on gas, rookie.
If you tried to bring your Venusian Vernian exploratorium ballooncraft for a jaunt across the skies of Jupiter, it would sink like a copper bowler with lead goggles.
The only thing that’s lighter than hydrogen is hot hydrogen. Let’s say you could make a balloon, and fill it with superheated hydrogen and float around the cloud tops of Jupiter suffering the crushing gravity. Is there anything else that might kill you?
Did you leave Earth? Then of course there is. Everything is going to kill you, always. You might want to write that on the brass plaque next to your ship’s wheel with the carving of Shiva in the center there, Captain Baron Cogsworth Copperglass.
Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Jupiter is surrounded by an enormous magnetic field, ten times more powerful than Earth’s. It traps particles and then whips them around like an accelerator. This radiation is a million times more powerful than the Earth’s Van Allen belts. Our big human meat roasting concern during the Apollo days.
If you tried to get near the radiation belts without insufficient shielding. It’d be bad. Just picture jamming your copper and brass steamwork fantasy into a giant microwave.
Is it possible there’s a solid core, deep down within Jupiter? Somewhere we could live, and not have to worry about those pesky buoyancy problems? Probably. Astronomers think there are a few times the mass of the Earth in rocky material deep down inside.
Of course, the pressure and temperature are incomprehensible. The temperature at the core of Jupiter is thought to be 24,000 degrees Celsius. Hydrogen is crushed so tightly it becomes superheated liquid or strange new flavors of ice. It becomes a metal.
The moral, we’re not equipped to go there. Let alone set up shop. So, let’s just stick with fantasizing your adventures as Emperor Esquire Beardweirdy Brassnozzle Steamypantaloons.
In his classic book 2001, Arthur C. Clarke said that “all these worlds are yours except Europa, attempt no landing there”. Well that’s crazy.
Europa’s awesome, we’re totally landing there, especially if we discover alien whales. So, Europa first. Besides, it’s just a book. So, Jupiter is the worst. Do not navigate your airship into that harbour.
What’s the worst possible environment you can imagine to try and live on? Tell us in the comments below.
Visualization of the radiation belts with confined charged particles (blue & yellow) and plasmapause boundary (blue-green surface). Image Credit:
NASA/Goddard
It’s a well-known fact that Earth’s ozone layer protects us from a great deal of the Sun’s ultra-violet radiation. Were it not for this protective barrier around our planet, chances are our surface would be similar to the rugged and lifeless landscape we observe on Mars.
Beyond this barrier lies another – a series of shields formed by a layer of energetic charged particles that are held in place by the Earth’s magnetic field. Known as the Van Allen radiation belts, this wall prevents the fastest, most energetic electrons from reaching Earth.
And according to new research from NASA’s Van Allen probes, it now appears that these belts may be nearly impenetrable, a finding which could have serious implications for future space exploration and research.
The existence of a belt of charged particles trapped by the Earth’s magnetosphere has been the subject of research since the early 20th century. However, it was not until 1958 that the Explorer 1 and Explorer 3 spacecrafts confirmed the existence of the belt, which would then be mapped out by the Explorer 4, Pioneer 3, and Luna 1 missions.
Two giant belts of radiation surround Earth. The inner belt is dominated by protons and the outer one by electrons. Credit: NASA
Since that time, scientists have discovered much about this belt, including how it interacts with other fields around our planet to form a nearly-impenetrable barrier to incoming electrons.
This discovery was made using NASA’s Van Allen Probes, launched in August 2012 to study the region. According to the observations made by the probes, this region 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.
“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.
In the decades since they were first discovered, scientists have learned that the size of the two belts can change – or merge, or even separate into three belts occasionally. But generally the inner belt stretches from 644 km to 10,000 km (400 – 6,000 mi) above the Earth’s surface while the outer belt stretches from 13,500 t0 58,000 km (8,400 – 36,000 mi).
Artist’s rendition of Van Allen Probes A and B in Earth orbit. Credit: NASA
Up until now, scientists have wondered why these two these belts have existed separately. Why, they have wondered, is there a fairly empty space between the two that appears to be free of electrons? That is where the newly discovered barrier comes in.
The Van Allen Probes data showed that the inner edge of the outer belt is, in fact, highly pronounced. For the fastest, highest-energy electrons, this edge is a sharp boundary that, under normal circumstances, cannot be penetrated.
“When you look at really energetic electrons, they can only come to within a certain distance from Earth,” said Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-author on the Nature paper. “This is completely new. We certainly didn’t expect that.”
The team looked at possible causes. They determined that human-generated transmissions were not the cause of the barrier. They also looked at physical causes, asking if the shape of the Earth’s magnetic field could be the cause of the boundary. However, NASA scientists studied and eliminated that possibility and determined that the presence of other space particles appears to be the more likely cause.
A cloud of cold, charged gas around Earth called the plasmasphere (seen here in purple), interacts with the particles in Earth’s radiation belts (shown in grey). Image Credit: NASA/Goddard
The radiation belts are not the only particle structures surrounding Earth. A giant cloud of relatively cool, charged particles called the plasmasphere fills the outermost region of Earth’s atmosphere, beginning at about 600 miles up and extending partially into the outer Van Allen belt. The particles at the outer boundary of the plasmasphere cause particles in the outer radiation belt to scatter, removing them from the belt.
This scattering effect is fairly weak and might not be enough to keep the electrons at the boundary in place, except for a quirk of geometry – the radiation belt electrons move incredibly quickly, but not toward Earth. Instead, they move in giant loops around Earth.
The Van Allen Probes’ data show that in the direction toward Earth, the most energetic electrons have very little motion at all – just a gentle, slow drift that occurs over the course of months. This movement is so slow and weak that it can be rebuffed by the scattering caused by the plasmasphere.
This also helps explain why – under extreme conditions, when an especially strong solar wind or a giant solar eruption such as a coronal mass ejection sends clouds of material into near-Earth space – the electrons from the outer belt can be pushed into the usually-empty slot region between the belts.
“The scattering due to the plasmapause is strong enough to create a wall at the inner edge of the outer Van Allen Belt,” said Baker. “But a strong solar wind event causes the plasmasphere boundary to move inward.”
A massive inflow of matter from the sun can erode the outer plasmasphere, moving its boundaries inward and allowing electrons from the radiation belts the room to move further inward too.
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 in NASA’s Living With a Star program, managed by Goddard.
A paper on these results appeared in the Nov. 26, 2014, issue of Nature magazine. And be sure to watch this animated video produced by the Goddard Space Center that explains the Van Allen belt in brief:
Illustration of the twin Van Allen Probes (formerly Radiation Belt Storm Probes) in orbit (JHUAPL/NASA)
Earth’s inner radiation belt displays a curiously zebra-esque striped pattern, according to the latest findings from NASA’s twin Van Allen Probes. What’s more, the cause of the striping seems to be the rotation of the Earth itself — something that was previously thought to be impossible.
“…it is truly humbling, as a theoretician, to see how quickly new data can change our understanding of physical properties.”
– Aleksandr Ukhorskiy, Johns Hopkins University Applied Physics Laboratory
Our planet is surrounded by two large doughnut-shaped regions of radiation called the Van Allen belts, after astrophysicist James Van Allen who discovered their presence in 1958. (Van Allen died at the age of 91 in 2006.) The inner Van Allen belt, extending from about 800 to 13,000 km (500 to 8,000 miles) above the Earth, contains high-energy electrons and protons and poses a risk to both spacecraft and humans, should either happen to spend any substantial amount of time inside it.
The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) is a time-of-flight versus energy spectrometer (JHUAPL)
Launched aboard an Atlas V rocket from Cape Canaveral AFS on the morning of Aug. 30, 2012, the Van Allen Probes (originally the Radiation Belt Storm Probes) are on a two-year mission to investigate the belts and find out how they behave and evolve over time.
One of the instruments aboard the twin probes, the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE), has detected a persistent striped pattern in the particles within the inner belt. While it was once thought that any structures within the belts were the result of solar activity, thanks to RBSPICE it’s now been determined that Earth’s rotation and tilted magnetic axis are the cause.
“It is because of the unprecedented high energy and temporal resolution of our energetic particle experiment, RBSPICE, that we now understand that the inner belt electrons are, in fact, always organized in zebra patterns,” said Aleksandr Ukhorskiy of the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Md., co-investigator on RBSPICE and lead author of the paper. “Furthermore, our modeling clearly identifies Earth’s rotation as the mechanism creating these patterns. It is truly humbling, as a theoretician, to see how quickly new data can change our understanding of physical properties.”
The model of the formation of the striped patterns is likened to the pulling of taffy.
RBSPICE data of stripes within the inner Van Allen belt (Click for animation) Credit: A. Ukhorskiy/JHUAPL
“If the inner belt electron populations are viewed as a viscous fluid,” Ukhorskiy said, “these global oscillations slowly stretch and fold that fluid, much like taffy is stretched and folded in a candy store machine.”
“This finding tells us something new and important about how the universe operates,” said Barry Mauk, a project scientist at APL and co-author of the paper. “The new results reveal a new large-scale physical mechanism that can be important for planetary radiation belts throughout the solar system. An instrument similar to RBSPICE is now on its way to Jupiter on NASA’s Juno mission, and we will be looking for the existence of zebra stripe-like patterns in Jupiter’s radiation belts.”
Jupiter’s Van Allen belts are similar to Earth’s except much larger; Jupiter’s magnetic field is ten times stronger than Earth’s and the radiation in its belts is a million times more powerful (source). Juno will arrive at Jupiter in July 2016 and spend about a year in orbit, investigating its atmosphere, interior, and magnetosphere.
Thanks to the Van Allen Probes. Juno now has one more feature to look for in Jupiter’s radiation belts.
“It is amazing how Earth’s space environment, including the radiation belts, continue to surprise us even after we have studied them for over 50 years. Our understanding of the complex structures of the belts, and the processes behind the belts’ behaviors, continues to grow, all of which contribute to the eventual goal of providing accurate space weather modeling.”
– Louis Lanzerotti, physics professor at the New Jersey Institute of Technology and principal investigator for RBSPICE
The Van Allen Probes are the second mission in NASA’s Living With a Star program, managed by NASA’s Goddard Space Flight Center in Greenbelt, MD. The program explores aspects of the connected sun-Earth system that directly affect life and society.
Artist's conception of NASA’s Van Allen Probes twin spacecraft. Credit: Andy Kale, University of Alberta
The radiation-heavy Van Allen Belts around Earth contain particles that can move at almost the speed of light across vast distances, new research reveals. The information came from an instrument flown aboard the Van Allen Probes twin NASA spacecraft, which launched in 2012.
According to scientists, the process that creates this is similar to what happens in the Large Hadron Collider and other particle accelerators. The magnetic field on the Earth accelerates electrons faster as these particles orbit the planet. While scientists had spotted this process happening at small scales before, the new paper has seen this across hundreds of thousands of kilometers or miles.
“With the Van Allen Probes, I like to think there’s no place for these particles to hide because each spacecraft is spinning and ‘glimpses’ the entire sky with its detector ‘eyes’, so we’re essentially getting a 360-degree view in terms of direction, position, energy, and time,” stated Harlan Spence, principal scientist for the Energetic Particle, Composition, and Thermal Plasma (ECT) instrument aboard the probes, and co-author on the research paper. He is also director of the University of New Hampshire Institute for the Study of Earth, Oceans, and Space.
The research was led by University of Alberta physicist Ian Mann, and is available in Nature Communications. “People have considered that this acceleration process might be present but we haven’t been able to see it clearly until the Van Allen Probes,” Mann stated.
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. Credit: NASA/Van Allen Probes/Goddard Space Flight Center
In September of 2012, scientists with the newly launched Van Allen Probes got permission to turn on one of their instruments after only three days in space instead of waiting for weeks, as planned. They wanted to turn on the Relativistic Electron Proton Telescope (REPT) so 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.
Now, they are very glad they did, as something happened that no one had ever seen before. A previously unknown third radiation belt formed in the Van Allen Radiation Belts that encircle Earth. The scientist watched – in disbelief – while their data showed the extra belt forming, then suddenly disappear, like it had been cut away with a knife. They have not yet seen a recurrence of a third belt.
“First we thought our instruments weren’t working correctly,” said Dan Baker, a member of the Van Allen Probes team from the University of Colorado at Boulder, “but we quickly realized we were seeing a real phenomenon.”
What happened is that shortly before REPT was turned on, solar activity on the Sun had sent energy toward Earth that caused the radiation belts to swell. The energetic particles then settled into a new configuration, showing an extra, third belt extending out into space.
“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 mission. “The third belt persisted beautifully, day after day, week after week, for four weeks.”
This graph shows energetic electron data gathered by the Relativistic Electron-Proton Telescope (REPT) instruments, on the twin Van Allen Probes satellites in eccentric orbits around the Earth, from Sept. 1, 2012 to Oct. 4, 2012 (horizontal axis). It shows three discrete energy channels (measured in megaelectron volts, or MeV). The third belt region (in yellow) and second slot (in green) are highlighted, and exist up until a coronal mass ejection (CME) destroys them on Oct. 1. The vertical axis in each is L*, effectively the distance in Earth radii at which a magnetic field line crosses the magnetic equatorial plane. Credit: LASP
Since their discovery in 1958, we’ve known that the Van Allen radiation belt is composed of two donut-shaped layers of energetic charged particles around the planet Earth, held in place by its magnetic field.
The scientists are now incorporating what they saw into new models of the radiation 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 human space flight.
The belts are normally between 200 to 60,000 kilometers above Earth; the new ring was much further out.
Launched on August 30, 2012 as the Radiation Belt Storm Probes mission, the twin probes were renamed in honor of the belts’ discoverer, astrophysicist James Van Allen. Observations of the belts have shown they are dynamic and mysterious. However, this type of dynamic three-belt structure was never seen, or even considered, theoretically.
A coronal mass ejection (CME) from the Sun on August 31, 2012, the event that caused a third ring to form in the Van Allen radiation belts. Credit: NASA
The Energetic Particle, Composition, and Thermal Plasma (ECT) suite of instruments on board the probes were designed to help understand how populations of electrons moving at nearly the speed of light and penetrating ions in space form or change in response to variable inputs of energy from the Sun.
Already, what the team has learned is re-writing the textbooks of what is known about the Van Allen belts.
“These events we’ve recorded are extraordinary and are already allowing us to refine and confirm our theories of belt dynamics in a way that will lead to predictability of their behavior,” said astrophysicst Harlan Spence, principal investigator for the ECT, “which is important for understanding space weather and ultimately for the safety of astronauts and spacecraft that operate within such a hazardous region of geospace.”
At a press briefing today, the team was asked why this third ring had never been observed before.
“We’ve never had the capability before to see something like this, said Nicky Fox, Van Allen Probes deputy project scientist. “The fact that we had such an amazing discovery within days of turning them on shows we still have mysteries to discover and explain. What the Van Allen Probes have shown is that the advances in technology and detection made by NASA have already had an almost immediate impact on basic science.”
Baker added, “As the philosopher Yogi Bera once said, you can observe a lot just by looking. This shows that when you open new eyes on the Universe you can invariably find new things.”
The team will be seeking to understand what the third ring mean for astronauts and satellites, even though the new ring is farther out, the regions in Earth orbit are magnetically connected to the new region that formed.
“Knowing more about this and understanding more about the belt is important for having better models and being able to predict the lifetimes of spacecraft,” said Fox.
“The rings, satellites, the space station are all affected by space weather,” said Mona Kessel, Van Allen Probes program scientist. “We don’t completely understand what we’ve seen, but we are modeling it and trying to piece this all together, so stay tuned.”
The team has published a paper in the journal Science.
The recently launched Radiation Belt Storm Probes (RBSP) mission, which is studying the Van Allen radiation belts, has now been renamed in honor of the late James Van Allen, who discovered the radiation belts encircling Earth in 1958.
“James Van Allen was a true pioneer in astrophysics,” said John Grunsfeld, astronaut and associate administrator for NASA’s Science Mission Directorate at the agency’s headquarters in Washington. “His ground breaking research paved the way for current and future space exploration. These spacecraft now not only honor his iconic name but his mark on science.”
During his career, Van Allen was the principal investigator for scientific investigations on 24 Earth satellites and planetary missions, beginning with the first successful American satellite, Explorer I, and continuing with Pioneer 10 and Pioneer 11. He also helped develop the first plans for an International Geophysical Year was held in 1957. Van Allen, who worked at APL during and after World War II, also is credited with discovery of a new moon of Saturn in 1979, as well as radiation belts around that planet.
Artist concept of the Van Allen Probes. Credit: NASA
Launched Aug. 30, 2012 from Cape Canaveral Air Force Station in Florida, the Van Allen Probes comprise the first dual-spacecraft mission specifically created to investigate the radiation belts that surround Earth. These two belts encircle the planet and are filled with highly charged particles.
The belts are affected by solar storms and coronal mass ejections and sometimes swell dramatically. When this occurs, they can pose dangers to communications, GPS satellites and human spaceflight activities.
“After only two months in orbit, the Van Allen Probes have made significant contributions to our understanding of the radiation belts,” says APL Director Ralph Semmel. “The science and data from these amazing twin spacecraft will allow for more effective and safe space technologies in the decades to come. APL is proud to have built and to operate this new resource for NASA and our nation, and we are proud to have the mission named for one of APL’s original staff.”
