"I'm drawn to extreme scenarios," said Luke Oman, a climate scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. Perhaps the most extreme scenario in his portfolio is nuclear conflict. Using a NASA computer simulation, Oman and colleagues model the climate's response to the smoke from fires brought about by regional nuclear war. His work, performed with colleagues at Rutgers University prior to joining NASA, is part of a larger panel discussing the issue on Feb. 18 at the meeting of the American Association for the Advancement of Science (AAAS) in Washington.

NASA: How were you turned on to this line of research?

Oman: The idea was spawned at a 2005 meeting of the American Geophysical Union, where I presented my research from Rutgers University on the subject of volcanoes.

Specifically, that work used computer simulations to model how sulphur dioxide gas ejected from volcanoes is converted into solid sulfate particles and then circulated in the upper atmosphere where it can impact climate.

While we were at the conference, some colleagues asked if the model could be modified to simulate black carbon aerosols emitted during a nuclear conflict, to illustrate the resulting impact on climate.

NASA: Has this been attempted before?

Oman: Yes, researchers started in the 1980s to look at the impacts from large-scale nuclear conflict scenarios.

More recently, with the emergence of smaller nuclear states, we wanted to make estimates of regional-scale conflicts. What kind of climate anomalies would we see? How would growing seasons change? My talk at the AAAS meeting, for example, is geared toward regional war and the potential impacts on global temperature and precipitation.

But it wasn't until about 10 years ago that the models became comprehensive enough to tackle these questions in a fully coupled way.

NASA: How do you go about simulating climate impacts of nuclear conflict?

Oman: With modeling we can find out some interesting aspects about the impact of aerosols on the underlying atmospheric dynamics and what's controlling their transport and removal.

We used a general circulation model, ModelE, from NASA's Goddard Institute for Space Studies in New York. ModelE is a coupled ocean-atmosphere model that shows how various inputs — in our case black carbon — would affect global climate.

Without this model the work wouldn't be possible. That's because it was one of the very few models that had a coupled atmosphere and ocean along with interactive aerosols, to be able to more fully address this issue then ever before.

NASA: What did the model reveal?

Oman: Instead of sulfate particles, like you get from a volcanic eruption, a nuclear event produces soot, and that results in very different climate impacts. Whereas sulfate particles from a volcano might warm the air of the upper atmosphere by a couple degrees, black carbon absorbs heat from the sun and can lead to much more atmospheric warming.

Sulfate and soot also vary in their impact on temperature at Earth's surface. That's because the particles differ in the amount of solar energy that they prevent from reaching the ground.

NASA: How does surface temperature change?

Oman: We studied the scenario of using 100 Hiroshima-size bombs, the fires from which would inject upward of 5 teragrams (megatons) of black carbon particles into Earth's upper troposphere. Observations of forest fires have shown this to occur on much smaller scales.

On the ground, global temperatures would fall by a little over 1 degree Celsius (C) (1.8 Fahrenheit (F)) over first three years. In contrast, aerosols from the 1991 eruption of Mount Pinatubo contributed to about 3/10 of a degree C (~ 0.5 F) of cooling over one year. Black carbon particles are smaller than sulfate particles and can be lofted much higher by solar heating, where their influence on climate can last up to a decade.

We also saw that two to four years after the event, rainfall would decrease globally by an average of about 10 percent.

As my colleagues Michael Mills [National Center for Atmospheric Research in Boulder, Colo.] and Brian Toon [University of Colorado at Boulder] are discussing at AAAS, the scenario also drives global stratospheric ozone loss and influences communities far away from the conflict. Agriculture, for example, would likely be disrupted from the combination of cooler temperatures, less precipitation and decreases in solar radiation reaching the surface. This would cause widespread interruptions to growing seasons by producing more frequent frosts.

NASA: How do you think this information is relevant for decision makers?

Oman: A primary goal of this work is to get the information revealed by our study into the hands of decision makers as well as to get other groups interested in this problem and to be aware of the potential impacts. Before we did this study, we didn't know what the climate anomalies would be or how long they would last. This is critical information that needs to be known in advance along with knowledge that the consequences of such a scenario would be global.

For more information visit http://www.nasa.gov/topics/earth/features/nuclear-climate.html

In November 2010, the scientific journal Icarus published a paper by astrophysicists John Matese and Daniel Whitmire, who proposed the existence of a binary companion to our sun, larger than Jupiter, in the long-hypothesized "Oort cloud" -- a faraway repository of small icy bodies at the edge of our solar system. The researchers use the name "Tyche" for the hypothetical planet. Their paper argues that evidence for the planet would have been recorded by the Wide-field Infrared Survey Explorer (WISE).

WISE is a NASA mission, launched in December 2009, which scanned the entire celestial sky at four infrared wavelengths about 1.5 times. It captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids and comets relatively close to Earth. Recently, WISE completed an extended mission, allowing it to finish a complete scan of the asteroid belt, and two complete scans of the more distant universe, in two infrared bands. So far, the mission's discoveries of previously unknown objects include an ultra-cold star or brown dwarf, 20 comets, 134 near-Earth objects (NEOs), and more than 33,000 asteroids in the main belt between Mars and Jupiter.

Following its successful survey, WISE was put into hibernation in February 2011. Analysis of WISE data continues. A preliminary public release of the first 14 weeks of data is planned for April 2011, and the final release of the full survey is planned for March 2012.

Frequently Asked Questions

Q: When could data from WISE confirm or rule out the existence of the hypothesized planet Tyche?

A: It is too early to know whether WISE data confirms or rules out a large object in the Oort cloud. Analysis over the next couple of years will be needed to determine if WISE has actually detected such a world or not. The first 14 weeks of data, being released in April 2011, are unlikely to be sufficient. The full survey, scheduled for release in March 2012, should provide greater insight. Once the WISE data are fully processed, released and analyzed, the Tyche hypothesis that Matese and Whitmire propose will be tested.

Q: Is it a certainty that WISE would have observed such a planet if it exists?

A: It is likely but not a foregone conclusion that WISE could confirm whether or not Tyche exists. Since WISE surveyed the whole sky once, then covered the entire sky again in two of its infrared bands six months later, WISE would see a change in the apparent position of a large planet body in the Oort cloud over the six-month period. The two bands used in the second sky coverage were designed to identify very small, cold stars (or brown dwarfs) -- which are much like planets larger than Jupiter, as Tyche is hypothesized to be.

Q: If Tyche does exist, why would it have taken so long to find another planet in our solar system?

A: Tyche would be too cold and faint for a visible light telescope to identify. Sensitive infrared telescopes could pick up the glow from such an object, if they looked in the right direction. WISE is a sensitive infrared telescope that looks in all directions.

Q: Why is the hypothesized object dubbed "Tyche," and why choose a Greek name when the names of other planets derive from Roman mythology?

A: In the 1980s, a different companion to the sun was hypothesized. That object, named for the Greek goddess "Nemesis," was proposed to explain periodic mass extinctions on the Earth. Nemesis would have followed a highly elliptical orbit, perturbing comets in the Oort Cloud roughly every 26 million years and sending a shower of comets toward the inner solar system. Some of these comets would have slammed into Earth, causing catastrophic results to life. Recent scientific analysis no longer supports the idea that extinctions on Earth happen at regular, repeating intervals. Thus, the Nemesis hypothesis is no longer needed. However, it is still possible that the sun could have a distant, unseen companion in a more circular orbit with a period of a few million years -- one that would not cause devastating effects to terrestrial life. To distinguish this object from the malevolent "Nemesis," astronomers chose the name of Nemesis's benevolent sister in Greek mythology, "Tyche."

JPL manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more information visit http://www.nasa.gov/mission_pages/WISE/news/wise20110218.html

Stars at all stages of development, from dusty little tots to young adults, are on display in a new image from NASA's Spitzer Space Telescope.

This cosmic community is called the North American nebula. In visible light, the region resembles the North American continent, with the most striking resemblance being the Gulf of Mexico. But in Spitzer's infrared view, the continent disappears. Instead, a swirling landscape of dust and young stars comes into view.

"One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible," said Luisa Rebull of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. Rebull is lead author of a paper about the observations, accepted for publication in the Astrophysical Journal Supplement Series. "The Spitzer image reveals a wealth of detail about the dust and the young stars here."

Rebull and her team have identified more than 2,000 new, candidate young stars in the region. There were only about 200 known before. Because young stars grow up surrounded by blankets of dust, they are hidden in visible-light images. Spitzer's infrared detectors pick up the glow of the dusty, buried stars.

A star is born inside a collapsing ball of gas and dust. As the material collapses inward, it flattens out into a disk that spins around together with the forming star like a spinning top. Jets of gas shoot perpendicularly away from the disk, above and below it. As the star ages, planets are thought to form out of the disk -- material clumps together, ultimately growing into mature planets. Eventually, most of the dust dissipates, aside from a tenuous ring similar to the one in our solar system, referred to as Zodiacal dust.

The new Spitzer image reveals all the stages of a star's young life, from the early years when it is swaddled in dust to early adulthood, when it has become a young parent to a family of developing planets. Sprightly "toddler" stars with jets can also be identified in Spitzer's view.

"This is a really busy area to image, with stars everywhere, from the North American complex itself, as well as in front of and behind the region," said Rebull. "We refer to the stars that are not associated with the region as contamination. With Spitzer, we can easily sort this contamination out and clearly distinguish between the young stars in the complex and the older ones that are unrelated."

The North American nebula still has a mystery surrounding it, involving its power source. Nobody has been able to identify the group of massive stars that is thought to be dominating the nebula. The Spitzer image, like images from other telescopes, hints that the missing stars are lurking behind the Gulf of Mexico portion of the nebula. This is evident from the illumination pattern of the nebula, especially when viewed with the detector on Spitzer that picks up 24-micron infrared light. That light appears to be coming from behind the Gulf of Mexico's dark tangle of clouds, in the same way that sunlight creeps out from behind a rain cloud.

The nebula's distance from Earth is also a mystery. Current estimates put it at about 1,800 light-years from Earth. Spitzer will refine this number by finding more stellar members of the North American complex.

The Spitzer observations were made before it ran out of the liquid coolant needed to chill its longer-wavelength instruments. Currently, Spitzer's two shortest-wavelength channels (3.6 and 4.5 microns) are still working. The composite image shows light from both the infrared array camera and multiband imaging processor. Infrared light with a wavelength of 3.6 microns is color-coded blue; 8.0-micron light is green; and 24-micron light is red.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more information visit http://www.nasa.gov/mission_pages/spitzer/news/spitzer20110210.html

In communities all across the U.S., travelers that went to the moon and back with the Apollo 14 mission are living out their quiet lives. The whereabouts of more than 50 are known. Many, now aging, reside in prime retirement locales: Florida, Arizona and California. A few are in the Washington, D.C., area. Hundreds more are out there -- or at least, they were. And Dave Williams of NASA's Goddard Space Flight Center in Greenbelt, Md., wants to find them before it's too late.

The voyagers in question are not astronauts. They're "moon trees" -- redwood, loblolly pine, sycamore, Douglas fir, and sweetgum trees sprouted from seeds that astronaut Stuart Roosa took to the moon and back 40 years ago.

"Hundreds of moon trees were distributed as seedlings," says Williams, "but we don't have systematic records showing where they all went."

And though some of the trees are long-lived species expected to live hundreds or thousands of years, others have started to succumb to the pressures of old age, severe weather and disease. At least a dozen have died, including the loblolly pine at the White House and a New Orleans pine that was damaged by Hurricane Katrina and later removed.

To capture the vanishing historical record, Williams, a curator at the National Space Science Data Center, has been tracking down the trees, dead or alive.

His sleuthing started in 1996, prompted by an email from a third-grade teacher, Joan Goble, asking about a tree at the Camp Koch Girl Scout Camp in Cannelton, Ind. A simple sign nearby read "moon tree."

"At the time, I had never heard of moon trees," Williams says. "The sign had a few clues, so I sent a message to the NASA history office and found more bits and pieces on the web. Then I got in touch with Stan Krugman and got more of the story."

Krugman had been the U.S. Department of Agriculture Forest Service's staff director for forest genetics research in 1971. He had given the seeds to Roosa, who stowed them in his personal gear for the Apollo 14 mission. The seeds were symbolic for Roosa because he had fought wildfires as a smoke jumper before becoming an Air Force test pilot and then an astronaut.

The seeds flew in the command module that Roosa piloted, orbiting the moon 34 times while astronauts Alan Shepard Jr. and Edgar Mitchell walked -- and in Shepard's case, played a little golf -- on the moon.

Back then, biologists weren't sure the seeds would germinate after such a trip. Few experiments of this kind had been done. A mishap during decontamination procedures made the fate of the seeds even less certain: the canister bearing the seeds was exposed to vacuum and burst, scattering its contents.

But the seeds did germinate, and the trees seemed to grow normally. At Forest Service facilities, the moon trees reproduced with regular trees, producing a second generation called half-moon trees.

By 1975, the trees were ready to leave the Forest Service nurseries. One was sent to Washington Square in Philadelphia to be the first moon tree planted as part of the United States Bicentennial celebrations; Roosa took part in that ceremony. Another tree went to the White House. Many more were planted at state capitals, historic locations and space- and forestry-related sites across the country. Gerald Ford, then the president, called the trees "living symbol[s] of our spectacular human and scientific achievements."

When Williams could find no detailed records of which trees went where, he created a webpage to collect as much information as possible. A flurry of emails came in from people who either knew of or came upon the trees.

"About a year after I put the webpage up, someone contacted me and asked why I didn't have the moon tree at Goddard listed," he says. "I hadn't known it was there!" Goddard's moon tree is a sycamore, planted in 1977 next to the visitors' center.

Williams has so far listed trees in 22 states plus Washington, D.C., and Rio Grande do Sul, Brazil. In many cases, the trees' extraordinary pedigrees were recorded on plaques or in newspaper clippings commemorating the event. Whenever possible, Williams has posted photos of the trees.

Second-generation moon trees, also tracked by Williams, continue to be planted. On Feb. 9, 2005, the 34th anniversary of the Apollo 14 splashdown, a second-generation sycamore was dedicated at Arlington National Cemetery "in honor of Apollo astronaut Stuart A. Roosa and the other distinguished Astronauts who have departed our presence here on earth." At the invitation of Roosa’s family, both Williams and a group of students from Cannelton attended the ceremony.

Another sycamore was planted at the U.S. National Arboretum in Washington, D.C., on April 22 (Earth Day), 2009. And on Feb. 3, 2011, one was planted in Roosa's honor at the Infinity Science Center, which is under construction at NASA's Stennis Space Center in Mississippi.

Rosemary Roosa, the astronaut's daughter, attended the Stennis ceremony. Her father, she says, was a strong supporter of science and space exploration, and she hopes the trees will serve as a reminder of the accomplishments of the U.S. space program as well as an inspiration to "reach for the stars."

People who know of the special legacy of the trees periodically check on them and contact Williams if a tree gets sick or knocked down by a storm. "Sometimes, I get an email from someone who went to the site where the tree used to be, and it's just gone," he says. "There's no sign of it, and we don't know what happened."

"I think when people are aware of the heritage of the trees, they usually take steps to preserve them," Williams adds, recalling one tree that was nearly knocked down during a building renovation. "But sometimes people aren't aware. That's why we want to locate as many as we can soon. We want to have a record that these trees are -- or were -- a part of these communities, before they're gone."

For more information visit http://www.nasa.gov/topics/history/features/moon-trees.html

Who are we? Where do we come from? These are questions that scientists hope to find clues to by better understanding the composition and evolution of the universe.

NASA flies sophisticated space missions that can probe vast regions of space to detect spectral signatures, or fingerprints, of unknown materials.

Through the years, scientists have found that these materials are much more complicated than originally anticipated. Because conditions in space are vastly different from conditions on Earth, identifying extraterrestrial materials is extremely difficult. Recently, researchers have achieved a major milestone by adding a new capability to one of the world’s unique laboratory facilities.

Located at NASA’s Ames Research Center, Moffett Field, Calif., this specialized facility, called the Cosmic Simulation Chamber (COSmIC), integrates a variety of state-of-the-art instruments to allow scientists to form, process and monitor simulated space conditions for planetary and interstellar materials in the laboratory.

The chamber is the heart of the system. It recreates the extreme conditions that reign in space where average temperatures can be as low as 100 Kelvin (less than -170 degree Celsius!), densities are billionths of Earth's (of the order of 10-16 - 10-17) and interstellar molecules and ions are bathed in stellar ultraviolet and visible radiation.

"The harsh conditions of space are extremely difficult to reproduce in the laboratory, and have long hindered efforts to interpret and analyze observations from space," said Farid Salama, a space science researcher in the Astrophysics Branch at Ames.

The idea of building the COSmIC facility started as a Director’s Discretionary Fund (DDF) project initiated by Salama in 1996, and its realization represents a true success story for Ames’ DDF program. The facility resulted from collaboration between Ames space science researchers and Los Gatos research scientists as a Small Business Innovative Research (SBIR) contract awarded by NASA.

The team of space scientists and engineers, lead by Salama, designed and built this unique laboratory facility to gain a deeper understanding of the composition of our universe and of the evolution of galaxies, both major objectives of NASA’s space research program.

In 2003, Ames scientists delivered their first major milestone by coupling COSmIC with a cavity ringdown spectrometer, an extremely sensitive device that can detect the spectral fingerprint of matter at the molecular level.

Now, another major milestone has been achieved by coupling COSmIC with a time-of-flight mass spectrometer, an ultra-sensitive device that detects the mass of matter at the molecular level.

In the past, part of the problem that prevented scientists from identifying unknown matter was the inability to simulate space conditions in the gaseous state. Today, researchers can successfully simulate gas-phase environments similar to interstellar clouds, stellar envelopes or planetary atmospheres environments by expanding solids using a free jet spray.

“By doing this, we now can measure large carbon molecules, like polycyclic aromatic hydrocarbons (PAHs) and similar carbon species. This is a major accomplishment,” said Salama. “This type of new research truly pushes the frontiers of science toward new horizons, and illustrates NASA's important contribution to science,” he added.

Scientists will use this “far out” facility to address two key problems: First, they want to identify the nature of big aerosol particles that have been detected by Cassini in the atmosphere of Saturn's moon, Titan. The second problem they will study is the formation of interstellar grains in the outflow of carbon stars.

“We can now truly simulate in the laboratory the formation of carbon grains in the envelope of stars, a major problem in today’s astrophysics,” said Cesar Contreras a NASA Postdoctoral Program (NPP) fellow and a member of the research team.

“We begin with small carbon molecules, expose these molecules to high energy processing in COSmIC, expand them in a cold jet spray and detect them with our highly sensitive detectors,” added Contreras, who studies interstellar grains.

Funded by NASA’s Science Mission Directorate Astronomy and Physics Research and Analysis, Planetary Atmospheres and Cosmochemistry programs, this new facility will also study the very large aerosol particles that were seen by the Cassini spacecraft in the upper atmosphere of Titan.

“In the Cassini data we see evidence for large aerosols in the upper atmosphere of Titan that we plan to explain with COSmIC” said Claire Ricketts, another NASA NPP fellow and member of the team, who studies the composition of the atmosphere of Titan.

“Titan is an important body in our solar system because it helps us understand the conditions that existed on early Earth” added Ricketts. “Organic haze in the atmosphere of Titan is similar to haze in early Earth's air.”

To understand Cassini’s data, scientists need this very powerful, very sensitive new tool. They will begin their analysis by forming molecules and species in the lab, measuring them in situ (inside their environment without disturbing them), and then trying to match their identity to Titan’s unknown aerosol molecules.

“Titan’s upper atmosphere data shows a rich spectrum. We will recreate those data in the lab and compare them to Cassini’s data. If they fit, great. If not, we will try something else. We will know when we are coming close to understanding them. We now have the right tool to do this,” said Salama.

“One day we will talk about the details and the implications of the data, but today we are celebrating the new milestone in the completion of this unique tool,” concluded Salama.

The Astrophysics and Astrochemistry Laboratory is part of the Astrophysics Branch in the Space Science and Astrobiology Division. Scientists in the Astrophysics Branch perform a wide range of astronomy and astrophysics research focusing on the development of new space, airborne and ground-based laboratory instrumentation such as COSmIC and SOFIA, as well as laboratory simulation experiments. The Ames team includes Farid Salama (POC), Claire Ricketts (NPP), Cesar Contreras (NPP) and Robert Walker.

For More information visit http://www.nasa.gov/topics/technology/features/tofs.html

NASA's Time History of Events and Macroscale Interaction during Substorms (THEMIS) spacecraft combined with computer models have helped track the origin of the energetic particles in Earth's magnetic atmosphere that appear during a kind of space weather called a substorm. Understanding the source of such particles and how they are shuttled through Earth's atmosphere is crucial to better understanding the Sun's complex space weather system and thus protect satellites or even humans in space.

The results show that these speedy electrons gain extra energy from changing magnetic fields far from the origin of the substorm that causes them. THEMIS, which consists of five orbiting satellites, helped provide these insights when three of the spacecraft traveled through a large substorm on February 15, 2008. This allowed scientists to track changes in particle energy over a large distance. The observations were consistent with numerical models showing an increase in energy due to changing magnetic fields, a process known as betatron acceleration.

"The origin of fast electrons in substorms has been a puzzle," says Maha Ashour-Abdalla, the lead author of a Nature Physics paper that appeared online on January 30, 2011 on the subject and a physicist at the University of California, Los Angeles. "It hasn't been clear until now if they got their burst of speed in the middle of the storm, or from some place further away."

Substorms originate opposite the sun on Earth's "night side," at a point about a third of the distance to the moon. At this point in space, energy and particles from the solar wind store up over time. This is also a point where the more orderly field lines near Earth -- where they look like two giant ears on either side of the globe, a shape known as a dipole since the lines bow down to touch Earth at the two poles – can distort into long lines and sometimes pull apart and "reconnect." During reconnection, the stored energy is released in explosions that send particles out in all directions. But reconnection is a magnetic phenomenon and scientists don't know the exact mechanism that creates speeding particles from that phenomenon.

"For thirty years, one of the questions about the magnetic environment around Earth has been, 'how do magnetic fields give rise to moving, energetic particles?'" says NASA scientist Melvyn Goldstein, chief of the Geospace Physics Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md., and another author on the paper. "We need to know such things to help plan the next generation of reconnection research instruments such as the Magnetospheric MultiScale mission (MMS) due to launch in 2014. MMS needs to look in the right place and for the correct signatures of particle energization."

In the early 1980s, scientists hypothesized that the quick, high-energy particles might get their speed from rapidly changing magnetic fields. Changing magnetic fields can cause electrons to zoom along a corkscrew path by the betatron effect.

Indeed, electrons moving toward Earth from a substorm will naturally cross a host of changing magnetic fields as those long, stretched field lines far away from Earth relax back to the more familiar dipole field lines closer to Earth, a process called dipolarization. Betatron acceleration causes the particles to gain energy and speed much farther away from the initial reconnection site. But in the absence of observations that could simultaneously measure data near the reconnection site and closer to Earth, the hypothesis was hard to prove or contradict.

THEMIS, however, was specifically designed to study the formation of substorms. It launched with five spacecraft, which can be spread out over some 44,000 miles – a perfect tool for examining different areas of Earth's magnetic environment at the same time. Near midnight, on February 15, 2008, three of the satellites moving through Earth's magnetic tail, about 36,000 miles from Earth, traveled through a large substorm.

"I looked at the THEMIS data for that substorm," says Ashour-Abdalla, "and saw there was a direct correlation of the increased particle energy at the origin with the region of dipolarization nearer to Earth."

To examine the data, Ashour-Abdalla and a team of researchers from UCLA, Nanchang University in China, NASA Goddard Space Flight Center, and the University of Maryland, Baltimore, used their expertise with computer modeling to simulate the complex dynamics that occur in space. The team began with spacecraft data from an ESA mission called Cluster that was in the solar wind at the time of the substorm. Using these observations of the solar environment, they modeled large scale electric and magnetic fields in space around Earth. Then they modeled the future fate of the various particles observed.

When the team looked at their models they saw that electrons near the reconnection sites didn't gain much energy. But as they looked closer to Earth, where the THEMIS satellites were located, their model showed particles that had some ten times as much energy – just as THEMIS had in fact observed.

This is consistent with the betatron acceleration model. The electrons gain a small amount of energy from the reconnection and then travel toward Earth, crossing many changing magnetic field lines. These fields produce betatronic acceleration just as Kivelson predicted in the early 1980s, speeding the electrons up substantially.

"This research shows the great science that can be accomplished when modelers, theorists and observationalists join forces," says astrophysicist Larry Kepko, who is a deputy project scientist for the THEMIS mission at Goddard. "THEMIS continues to yield critical insights into the dynamic processes that produce the space weather that affects Earth."

Launched in 2007, THEMIS was NASA's first five-satellite mission launched aboard a single rocket. The unique constellation of satellites provided scientists with data to help resolve the mystery of how Earth's magnetosphere stores and releases energy from the sun by triggering geomagnetic substorms. Two of the satellites have been renamed ARTEMIS and are in the process of moving to a new orbit around the moon. They are due to reach their final lunar orbit in July 2011. The three remaining THEMIS satellites continue to study substorms.

THEMIS is managed by NASA's Goddard Space Flight Center for the agency's Science Mission Directorate. The Space Sciences Laboratory at the University of California, Berkeley, is responsible for project management, space and ground-based instruments, mission integration, mission operations and science. ATK (formerly Swales Aerospace), Beltsville, Md., built the THEMIS probes. THEMIS is an international project conducted in partnership with Germany, France, Austria, and Canada.

For more information visit http://www.nasa.gov/mission_pages/themis/news/speedy-particles.html