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  • richardmitnick 5:46 pm on February 12, 2019 Permalink | Reply
    Tags: , , , , Earth's Radiation Belts, , , NASA Van Allen Probes   

    From NASA Goddard Space Flight Center: “NASA’s Van Allen Probes Begin Final Phase of Exploration in Earth’s Radiation Belts” 

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    Feb. 12, 2019

    Geoff Brown
    Johns Hopkins University Applied Physics Lab

    Media contact: Karen C. Fox
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    Two tough, resilient, NASA spacecraft have been orbiting Earth for the past six and a half years, flying repeatedly through a hazardous zone of charged particles around our planet called the Van Allen radiation belts. The twin Van Allen Probes, launched in August 2012, have confirmed scientific theories and revealed new structures and processes at work in these dynamic regions. Now, they’re starting a new and final phase in their exploration.

    Van Allen Radiation belts from ESA INTEGRAL

    Van Allen Belts NASA GSFC

    NASA Van Allen Probes

    On Feb. 12, 2019, one of the twin Van Allen Probes begins a series of orbit descent maneuvers to bring its lowest point of orbit, called perigee, just under 190 miles closer to Earth. This will bring the perigee from about 375 miles to about 190 miles — a change that will position the spacecraft for an eventual re-entry into Earth’s atmosphere about 15 years down the line.

    “In order for the Van Allen Probes to have a controlled re-entry within a reasonable amount of time, we need to lower the perigee,” said Nelli Mosavi, project manager for the Van Allen Probes at the Johns Hopkins Applied Physics Laboratory, or APL, in Laurel, Maryland. “At the new altitude, aerodynamic drag will bring down the satellites and eventually burn them up in the upper atmosphere. Our mission is to obtain great science data, and also to ensure that we prevent more space debris so the next generations have the opportunity to explore the space as well.”

    The other of the two Van Allen Probes will follow suit in March, also commanded by the mission operations team at APL, which designed and built the satellites.

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    The twin Van Allen Probes have spent more than six years orbiting through Earth’s radiation belts. Orbit changes in early 2019 will ensure that the spacecraft eventually de-orbit and disintegrate in Earth’s atmosphere. Credits: NASA Goddard’s Scientific Visualization Studio

    The Van Allen Probes spend most of their orbit within Earth’s radiation belts: doughnut-shaped bands of energized particles — protons and electrons — trapped in Earth’s magnetic field. These fast-moving particles create radiation that can interfere with satellite electronics and could even pose a threat to astronauts who pass through them on interplanetary journeys. The shape, size and intensity of the radiation belts changes in response to solar activity, which makes predicting their state difficult.

    Originally designated as a two-year mission — based on predictions that no spacecraft could operate much longer than that in the harsh radiation belts — these rugged spacecraft have operated without incident since 2012, and continue to enable groundbreaking discoveries about the Van Allen Belts.


    Credits: NASA’s Goddard Space Flight Center

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    After performing de-orbit maneuvers in February and March 2019, the Van Allen Probes’ highly elliptical orbits will gradually tighten over the next 15-25 years as the spacecraft experience atmospheric drag at perigee, the point in their orbits closest to Earth. This atmospheric drag will pull them into a circular orbit as early as 2034, at which point the spacecraft will begin to enter Earth’s atmosphere and safely disintegrate. Credits: Johns Hopkins APL

    “The Van Allen Probes mission has done a tremendous job in characterizing the radiation belts and providing us with the comprehensive information needed to deduce what is going on in them,” said David Sibeck, mission scientist for the Van Allen Probes at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The very survival of these spacecraft and all their instruments, virtually unscathed, after all these years is an accomplishment and a lesson learned on how to design spacecraft.”

    Each spacecraft will be moved to a new, lower perigee of about 190 miles above Earth through a series of five two-hour engine burns. Because the Van Allen Probes spin while in orbit, the dates of these burns had to be chosen carefully. The needed geometry happens just once or twice per year: for spacecraft B, that period falls Feb. 12-22 of this year, and for spacecraft A, it’s March 11-22.

    The engine burns will each use about 4.4 pounds of propellant, leaving the spacecraft with enough fuel to keep their solar panels pointed at the Sun for about one more year.

    “We’ll continue to operate and obtain new science in our new orbit until we are out of fuel, at which point we won’t be able to point our solar panels at the Sun to power the spacecraft systems,” said Mosavi.

    During their last year or so of life, the Van Allen Probes will continue to gather data on Earth’s dynamic radiation belts. And their new, lower passes through Earth’s atmosphere will also provide new insight into how oxygen in Earth’s upper atmosphere can degrade satellite instruments — information that could help engineers design more resilient satellite instruments in the future.

    “The spacecraft and instruments have given us incredible insight into spacecraft operations in a high-radiation environment,” said Mosavi. “Everyone on the mission feels a real sense of pride and accomplishment in the work we’ve done and the science we’ve provided to the world — even as we begin the de-orbiting maneuvers.”

    Read more about what the Van Allen Probes have accomplished since 2012.

    For more on the Van Allen Probes: nasa.gov/vanallenprobes

    See the full article here.


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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


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  • richardmitnick 7:09 am on September 2, 2017 Permalink | Reply
    Tags: , NASA Van Allen Probes, Understand our near-Earth environment   

    From Goddard: “NASA’s Van Allen Probes Survive Extreme Radiation Five Years On” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Sept. 1, 2017
    Mara Johnson-Groh
    mara.johnson-groh@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    Most satellites, not designed to withstand high levels of particle radiation, wouldn’t last a day in the Van Allen Radiation belts. Trapped by Earth’s magnetic field into two giant belts around the planet, high-energy particles in the region can batter the spacecraft and even interfere with onboard electronics. But NASA’s Van Allen Probes have been traveling through this hazardous area since Aug. 30 2012 – they are now celebrating their fifth year in space studying this dynamic region.

    The Van Allen Probes mission is the second of NASA’s Living with a Star missions, which is tasked with understand our near-Earth environment. The two identical spacecraft, built with radiation-hardened components, study how high-energy particles are accelerated and lost from the belts. This information helps scientists understand and predict space weather, which, in addition to creating shimmering auroras, can disrupt power grids and GPS communications.

    “During its first five years, the Van Allen Probes have made enormously significant contributions to our understanding of radiation belt physics, including truly exceptional discoveries,” said Shri Kanekal, Van Allen Probes deputy mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

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    The two Van Allen Probes work as a team, following one behind the other to uniquely observe changes in the belts. Credits: NASA’s Goddard Space Flight Center/JHUAPL

    The Van Allen Probes mission has provided invaluable information about the very shape of the belts, discovering a third radiation belt that can appear during certain circumstances, and used uniquely capable instruments to unveil inner radiation belt features that were all but invisible to previous sensors. The mission has also extended beyond the practical considerations of the hazards of Earth’s space environment: Observations have found process that generate intense particle radiation inside the belts also occur across the universe, making the region a unique natural laboratory for developing our understanding of the particle energization processes.

    In celebration of the Van Allen Probes’ fifth year in space, here are five facts about the spacecraft.

    14+ gigabits – amount of data are downloaded daily from each spacecraft
    2,000 miles per hour – spacecrafts’ cruising speed
    164 feet – length of the longest instruments aboard the spacecraft
    3.8 square yards – size of solar panels used to power the instruments
    9 hours – time each spacecraft takes to encircle Earth

    Originally tasked with a two-year mission, the Van Allen Probes continue to make new discoveries five years on, continuing to solve scientific puzzles about the dynamic belt region around Earth.

    Related Links

    Learn more about the Van Allen Probes
    Learn more about the NASA’s Living with a Star Program

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


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  • richardmitnick 11:15 am on May 29, 2017 Permalink | Reply
    Tags: A bubble around Earth, , , , , , NASA Van Allen Probes   

    From COSMOS: “Radio signals may have created a protective magnetic bubble around Earth” 

    Cosmos Magazine bloc

    COSMOS

    29 May 2017
    No writer credit found.

    Very low frequency radio communications with deep-sea submarines may keep out high energy electrons and protons.

    2

    Very low frequency (VLF) radio communications – the kind we use to communicate with submarines, far below sea level – could be creating a bubble around Earth that protects against high levels of space radiation.

    NASA’s Van Allen Probes have observed the extent to which excess space radiation, in the form of highly-charged particles, moves into our near-Earth environment.

    Van Allen Belts NASA GSFC

    NASA Van Allen Probes

    A new paper at SpringerLink from researchers at the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder, US, observes that the outer limit of the bubble of radio waves around the planet caused by VLF communication is about the same as the inner limit of the Van Allen radiation belts – layers of charged particles held in place by Earth’s magnetic fields.

    The paper suggests that this may not be a coincidence – that perhaps our radio waves are impacting how particles move in space. Indeed, in the 1970s, before VLF communication was in widespread use, it appears radiation was present further into our near-Earth atmosphere.

    If this analysis is accurate, VLF transmission could be used to remove excess radiation from the Earth’s atmosphere. Further research is underway to test the impact of VLF transmissions on charged particles in our upper atmosphere.

    See the full article here .

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  • richardmitnick 6:54 am on May 20, 2017 Permalink | Reply
    Tags: , , , , MIT Haystack Observatory, NASA Van Allen Probes, , Van Allen Probes detect barrier around Earth, VLF - radio communications   

    From Spaceflight Insider: “Van Allen Probes detect barrier around Earth” 

    1

    Spaceflight Insider

    5.18.17
    Paul Knightly

    1
    The identical Van Allen Probes follow similar orbits that take them through both the inner and outer radiation belts. The highly elliptical orbits range from a minimum altitude of approximately 373 miles (600 kilometers) to a maximum altitude of approximately 23,000 miles (37,000 kilometers). Image & Caption Credit: NASA/JHU-APL

    New results from NASA’s Van Allen Probes have revealed the impact humans have on the environment is not limited to physical and chemical impacts on the Earth’s surface, but it also includes radio frequencies extending out into space. The probes have found that very low frequency, or VLF, radio communications interact with particles in space that can form an artificial barrier against high-energy particle radiation from space.

    The Van Allen radiation belts have been a fixture of the near-Earth space environment since their discovery at the start of the Space Age, but VLF communications have been a much more recent phenomenon that has seen increased use since the 1960s. VLF communications are primarily utilized to communicate with submarines across vast distances in the ocean from powerful ground stations.

    VLF communications were used on a limited basis in the 1960s, but they did not see widespread use until the latter portion of the Cold War. Despite these communications being directed in a downward direction, they can also extend above the surface creating a VLF bubble that is detectable by spacecraft.

    “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,” said Phil Erickson, assistant director at the MIT Haystack Observatory located in Westford, Massachusetts.

    What the Van Allen Probes have found is that the bubble produced by VLF frequencies corresponds with the inner extent of the Van Allen radiation belts. A comparison of modern data from the Van Allen belts with historical data from the 1960s shows that the Van Allen belt locations today are further from the Earth than they were 50 years ago.

    The ability of VLF radio transmissions to impact the near-Earth environment is being studied in further detail. Scientists are studying the possibility of using VLF transmissions in the upper atmosphere to help mitigate the effects of charged particles on spacecraft that are sensitive to major space weather events, such as coronal mass ejections from the Sun.

    See the full article here .

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    SpaceFlight Insider reports on events taking place within the aerospace industry. With our team of writers and photographers, we provide an “insider’s” view of all aspects of space exploration efforts. We go so far as to take their questions directly to those officials within NASA and other space-related organizations. At SpaceFlight Insider, the “insider” is not anyone on our team, but our readers.

    Our team has decades of experience covering the space program and we are focused on providing you with the absolute latest on all things space. SpaceFlight Insider is comprised of individuals located in the United States, Europe, South America and Canada. Most of them are volunteers, hard-working space enthusiasts who freely give their time to share the thrill of space exploration with the world.

     
  • richardmitnick 3:57 pm on August 15, 2016 Permalink | Reply
    Tags: , NASA Van Allen Probes,   

    From Goddard: “NASA’s Van Allen Probes Catch Rare Glimpse of Supercharged Radiation Belt” 

    NASA Goddard Banner

    NASA Goddard Space Flight Center

    Aug. 15, 2016
    Lina Tran
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    Our planet is nestled in the center of two immense, concentric doughnuts of powerful radiation: the Van Allen radiation belts, which harbor swarms of charged particles that are trapped by Earth’s magnetic field. On March 17, 2015, an interplanetary shock – a shockwave created by the driving force of a coronal mass ejection, or CME, from the sun – struck Earth’s magnetic field, called the magnetosphere, triggering the greatest geomagnetic storm of the preceding decade.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase
    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    And NASA’s Van Allen Probes were there to watch the effects on the radiation belts.

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    Artist concept of accelerated electrons circulating in Earth’s Van Allen radiation belts. Credits: NASA’s Goddard Space Flight Center; Tom Bridgman, animator

    NASA Van Allen Probes


    On March 17, 2015, an interplanetary shock – a shockwave created by the driving force of a coronal mass ejection, or CME, from the sun – struck the outermost radiation belt, triggering the greatest geomagnetic storm of the preceding decade. NASA’s Van Allen Probes were there to watch it. Credits: NASA’s Goddard Space Flight Center; Genna Duberstein, producer

    One of the most common forms of space weather, a geomagnetic storm describes any event in which the magnetosphere is suddenly, temporarily disturbed. Such an event can also lead to change in the radiation belts surrounding Earth, but researchers have seldom been able to observe what happens. But on the day of the March 2015 geomagnetic storm, one of the Van Allen Probes was orbiting right through the belts, providing unprecedentedly high-resolution data from a rarely witnessed phenomenon. A paper on these observations was published in the Journal of Geophysical Research on Aug. 15, 2016.

    Researchers want to study the complex space environment around Earth because the radiation and energy there can impact our satellites in a wide variety of ways – from interrupting onboard electronics to increasing frictional drag to disrupting communications and navigation signals.

    “We study radiation belts because they pose a hazard to spacecraft and astronauts,” said David Sibeck, the Van Allen Probes mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved with the paper. “If you knew how bad the radiation could get, you would build a better spacecraft to accommodate that.”

    Studying the radiation belts is one part of our efforts to monitor, study and understand space weather. NASA launched the twin Van Allen Probes in 2012 to understand the fundamental physical processes that create this harsh environment so that scientists can develop better models of the radiation belts. These spacecraft were specifically designed to withstand the constant bombardment of radiation in this area and to continue to collect data even under the most intense conditions. A set of observations on how the radiation belts respond to a significant space weather storm, from this harsh space environment, is a goldmine.

    The recent research describes what happened: The March 2015 storm was initiated by an interplanetary shock hurtling toward Earth – a giant shockwave in space set off by a CME, much like a tsunami is triggered by an earthquake.

    Swelling and shrinking in response to such events and solar radiation, the Van Allen belts are highly dynamic structures within our planet’s magnetosphere. Sometimes, changing conditions in near-Earth space can energize electrons in these ever-changing regions. Scientists don’t yet know whether energization events driven by interplanetary shocks are common. Regardless, the effects of interplanetary shocks are highly localized events – meaning if a spacecraft is not precisely in the right place when a shock hits, it won’t register the event at all. In this case, only one of the Van Allen Probes was in the proper position, deep within the magnetosphere – but it was able to send back key information.

    The spacecraft measured a sudden pulse of electrons energized to extreme speeds – nearly as fast as the speed of light – as the shock slammed the outer radiation belt. This population of electrons was short-lived, and their energy dissipated within minutes. But five days later, long after other processes from the storm had died down, the Van Allen Probes detected an increased number of even higher energy electrons. Such an increase so much later is a testament to the unique energization processes following the storm.

    “The shock injected – meaning it pushed – electrons from outer regions of the magnetosphere deep inside the belt, and in that process, the electrons gained energy,” said Shri Kanekal, the deputy mission scientist for the Van Allen Probes at Goddard and the leading author of a paper on these results.

    Researchers can now incorporate this example into what they already know about how electrons behave in the belts, in order to try to understand what happened in this case – and better map out the space weather processes there. There are multiple ways electrons in the radiation belts can be energized or accelerated: radially, locally or by way of a shock. In radial acceleration, electrons are carried by low-frequency waves towards Earth. Local acceleration describes the process of electrons gaining energy from relatively higher frequency waves as the electrons orbit Earth. And finally, during shock acceleration, a strong interplanetary shock compresses the magnetosphere suddenly, creating large electric fields that rapidly energize electrons.

    Scientists study the different processes to understand what role each process plays in energizing particles in the magnetosphere. Perhaps these mechanisms occur in combination, or maybe just one at a time. Answering this question remains a major goal in the study of radiation belts – a difficult task considering the serendipitous nature of the data collection, particularly in regard to shock acceleration.

    Additionally, the degree of electron energization depends on the process that energizes them. One can liken the process of shock acceleration, as observed by the Van Allen Probe, to pushing a swing.

    “Think of ‘pushing’ as the phenomenon that’s increasing the energy,” Kanekal said. “The more you push a swing, the higher it goes.” And the faster electrons will move after a shock.

    In this case, those extra pushes likely led to the second peak in high-energy electrons. While electromagnetic waves from the shock lingered in the magnetosphere, they continued to raise the electrons’ energy. The stronger the storm, the longer such waves persist. Following the March 2015 storm, resulting electromagnetic waves lasted several days. The result: a peak in electron energy measured by the Van Allen Probe five days later.

    This March 2015 geomagnetic storm was one of the strongest yet of the decade, but it pales in comparison to some earlier storms. A storm during March 1991 was so strong that it produced long-lived, energized electrons that remained within the radiation belts for multiple years. With luck, the Van Allen Probes may be in the right position in their orbit to observe the radiation belt response to more geomagnetic storms in the future. As scientists gather data from different events, they can compare and contrast them, ultimately helping to create robust models of the little-understood processes occurring in these giant belts.

    The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, built and operates the Van Allen Probes for NASA’s Heliophysics Division in the Science Mission Directorate. The Van Allen Probes are the second mission in NASA’s Living With a Star program, an initiative managed by Goddard and focused on aspects of the sun-Earth system that directly affect human lives and society.

    Related Links

    Van Allen Probes Mission Overview
    NASA’s Van Allen Probes Spot an Impenetrable Barrier in Space
    NASA’s Van Allen Probes Revolutionize View of Radiation Belts

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

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  • richardmitnick 7:47 pm on March 2, 2016 Permalink | Reply
    Tags: , , NASA Van Allen Probes,   

    From LANL: “Study finds surprising variability in shape of Van Allen Belts” 

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    Los Alamos National Laboratory

    February 23, 2016
    Laura Mullane
    Communications Office
    (505) 667-6012
    mullane@lanl.gov

    Van Allen Belts NASA GSFC
    Depiction of the Van Allen Belts. NASA/GSFC

    Findings could impact how we protect technology in space

    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.

    NASA Van Allen Probes
    Van Allen probe

    “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. Los Alamos has been studying space weather and its effects on national security satellites since the 1960s, when the U.S. launched the Vela satellites to support nuclear treaty verification.

    Since scientists first began forming a picture of these rings of energetic particles in the 1950s, understanding of their shape has largely remained unchanged—a small, inner belt, a largely empty space known as the slot region, and then the outer belt, which is dominated by electrons and is larger and more dynamic than the others.

    But this new analysis reveals that the shape varies from a single, continuous belt with no slot region, to a larger inner belt with a smaller outer belt, to no inner belt at all. Many of the differences are accounted for by considering electrons at different energy levels separately.

    “It’s like listening to different parts of a song,” said Reeves. “The bass line sounds different from the vocals, and the vocals are different from the drums, and so on.”

    The authors of the study, from Los Alamos National Laboratory and the New Mexico Consortium, found that the inner belt—the smaller belt in the classic picture of the belts—is much larger than the outer belt when observing electrons with low energies, while the outer belt is larger when observing electrons at higher energies. At the very highest energies, the inner belt structure is missing completely. So, depending on what one focuses on, the radiation belts can appear to have very different structures simultaneously.

    These structures are further altered by geomagnetic storms. When high-speed solar wind streams or coronal mass ejections—fast-moving magnetic material from the sun—collide with Earth’s magnetic field, they send it oscillating, creating a geomagnetic storm. Geomagnetic storms can increase or decrease the number of energetic electrons in the radiation belts for days to months, though the belts return to their normal configuration after a time.

    These storm-driven electron increases and decreases are currently unpredictable, without a clear pattern showing what type or strength of storm will yield what outcomes. There’s a saying in the space physics community: if you’ve seen one geomagnetic storm, you’ve seen one geomagnetic storm. But, it turns out, those observations have largely been based on electrons at only a few energy levels.

    “When we look across a broad range of energies, we start to see some consistencies in storm dynamics,” said Reeves. “The electron response at different energy levels differs in the details, but there is some common behavior. For example, we found that electrons fade from the slot regions quickly after a geomagnetic storm, but the location of the slot region depends on the energy of the electrons.”

    Often, the outer electron belt expands inwards toward the inner belt during geomagnetic storms, completely filling in the slot region with lower-energy electrons and forming one huge radiation belt. At lower energies, the slot forms farther from Earth, producing an inner belt that is bigger than the outer belt. At higher energies, the slot forms closer to Earth, reversing the comparative sizes.

    The twin Van Allen Probes satellites expand the range of energetic electron data we can capture. In addition to studying the extremely high-energy electrons—carrying millions of electron volts—that had been studied before, the Van Allen Probes can capture information on lower-energy electrons that contain only a few thousand electron volts. Additionally, the spacecraft measure radiation belt electrons at a greater number of distinct energies than was previously possible.

    “Previous instruments would only measure five or ten energy levels at a time,” said Reeves. “But the Van Allen Probes measure hundreds.”

    Measuring the flux of electrons at these lower energies has proved difficult in the past because of the presence of protons in the radiation belt regions closest to Earth. These protons shoot through particle detectors, creating a noisy background from which the true electron measurements needed to be picked out. But the higher-resolution Van Allen Probes data found that these lower-energy electrons circulate much closer to Earth than previously thought.

    “Despite the proton noise, the Van Allen Probes can unambiguously identify the energies of the electrons they’re measuring,” said Reeves.

    Precise observations like this, from hundreds of energy levels, rather than just a few, will allow scientists to create a more precise and rigorous model of what, exactly, is going on in the radiation belts, both during geomagnetic storms and during periods of relative calm.

    “You can always tweak a few parameters of your theory to get it to match observations at two or three energy levels,” said Reeves. “But having observations at hundreds of energies constrain the theories you can match to observations.”

    Los Alamos co-authors of the paper are Reiner Friedel, Brian Larsen, Ruth Skoug, and Herbert Funsten. The co-author from the New Mexico Consortium is Mick Denton. The higher energy electron data came from the Magnetic Electron Ion Spectrometer (MagEIS) built by The Aerospace Corp. The lower energy electron data come from the Helium Oxygen Proton Electron (HOPE) spectrometer, which was designed and built at Los Alamos. The Johns Hopkins Applied Physics Laboratory in Laurel, Md., built and operates the Van Allen Probes for NASA’s Science Mission Directorate. The mission is the second mission in NASA’s Living With a Star program, managed by NASA’s Goddard Space Flight Center in Greenbelt, Md.

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    Los Alamos National Laboratory’s mission is to solve national security challenges through scientific excellence.

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    Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.

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  • richardmitnick 4:45 pm on January 19, 2016 Permalink | Reply
    Tags: , , Hiss in the atmosphere, NASA Van Allen Probes   

    From Eos: “New Clues to Mysterious Hiss in Earth’s Plasmasphere” 

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    Eos

    26 October 2015 [Just brought forward]
    Mark Zastrow

    NASA Van Allen Probes
    NASA Van Allen Probes in orbit within Earth’s magnetic field. Credit: JHU/APL

    In space, no one can hear you scream—but if you have the right radio equipment, you can “hear” the electromagnetic waves undulating through the void. Now, scientists have found previously unheard signals in this static that might help them uncover the source of a particular kind of hiss.

    All of the waves examined in this study were generated by the particles of plasma trapped in Earth’s magnetic field. They spiral, gyrate, resonate, and stock up energy and release it—which creates tiny ripples in the electric and magnetic field surrounding Earth. When these waves are converted to sound—like a radio playing FM broadcasts—the space around Earth sounds like a jungle filled with different species of particles and electromagnetic behaviors, all emitting distinctive calls. For example, lightning can trigger waves called whistlers, which, as the name suggests, sound like whistling falling tones. Spectacular auroral displays amplify the so-called dawn chorus—chirpy waves that sound similar to birds in the morning. [Visit the full article for a sound bite of the hiss at this point.]

    One of the most mysterious of these noises is plasmaspheric hiss—an ever-present sibilance in the inner regions of Earth’s magnetic field. It sounds like pure static spanning 100 Hz to several kilohertz, a frequency range roughly equivalent to that produced by the middle third of a piano. Scientists know that plasmaspheric hiss plays a crucial role in shaping the structure of Earth’s radiation belts, disrupting them by knocking their energetic particles out into the atmosphere.

    However, the source of the hiss is unknown. One theory says that it is the direct result of spiraling electrons high over Earth’s equator. Others propose that it consists of the remnants of distant whistlers or chorus waves that devolve into incoherence, like the expressionless chop far out at sea.

    Previously, scientists assumed that this hiss was random white noise with no coherent features. However, when Summers et al. analyzed NASA satellite measurements of the hiss from 2013, they found something quite different. After breaking down the noise into its spectrum of frequencies, they discovered barely detectable rising and falling tones similar to the whistlers, at frequencies rising to roughly middle C and falling for about two octaves. The authors say that this detection was made possible by the high resolution of the instruments on the satellites, NASA’s Van Allen Probes, and their particularly useful orbit, which keeps them mostly within Earth’s radiation belts.

    Although the waves within plasmaspheric hiss resemble whistler tones and may share similarities in mathematical wave theory, the physical mechanism that generates the hiss is still wide open for debate. The authors expect that this fine structure will renew interest in the subject and may contain the clues to pin down its source. (Journal of Geophysical Research: Space Physics, doi:10.1002/2014JA020437, 2014)

    —Mark Zastrow, Freelance Writer

    Citation: Zastrow, M. (2015), New clues to mysterious hiss in Earth’s plasmasphere, Eos, 96, doi:10.1029/2015EO037985. Published on 26 October 2015.

    See the full article here .

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

     
  • richardmitnick 9:29 am on December 11, 2014 Permalink | Reply
    Tags: , , , , , NASA Van Allen Probes   

    From NASA Goddard: “NASA’s Van Allen Probes Discover a Surprise Circling Earth” 

    NASA Goddard Banner

    February 28, 2013
    Karen C. Fox
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    Since their discovery over 50 years ago, the Earth’s Van Allen radiation belts have been considered to consist of two distinct zones of trapped, highly energetic charged particles. Observations from NASA’s Van Allen Probes reveal an isolated third ring in the outer radiation belt.
    Image Credit: NASA/Goddard Space Flight Center

    NASA Van Allen Probes
    NASA/Van Allen Probes

    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.

    NASA Van Allen Probe Relativistic Electron Proton Telescope (REPT)
    NASA/REPT

    NASA SAMPEX
    NASA/SAMPEX

    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.

    v
    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.
    Image Credit: NASA/Van Allen Probes/Goddard Space Flight Center

    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.”

    f
    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).
    Image Credit: NASA/SDO/AIA/Goddard Space Flight Center

    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.”

    The Johns Hopkins University Applied Physics Laboratory (APL) built and operates the twin Van Allen Probes. The Van Allen Probes comprise the second mission in NASA’s Living With a Star (LWS) program to explore aspects of the connected sun-Earth system that directly affect life and society. The program is managed by NASA Goddard.

    See the full article, with video, here.

    Please help promote STEM in your local schools.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA Goddard Campus
    NASA/Goddard Campus
    NASA

     
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