March 9, 2017:

UCLA EPSS novel aurora findings chosen for JGR cover art:

"UCLA EPSS research findings are featured on the February 2017 cover of the Journal of Geophysical Research: Space Physics. The study describes the properties of a newly discovered form of the northern lights, called throat aurora, on the dayside of Earth facing the sun (upward, out of frame). Using observations on the ground and in interplanetary space, the aurora are postulated to form through a novel combination of plasma flows inside and outside of the Earth's magnetic field (the magnetosphere). Under certain conditions, solar wind interactions at the bow shock (~2 Earth widths upstream of the magnetosphere) can produce fast jets of hot plasma that perturb the outer boundary of the magnetosphere, as shown by previous UCLA EPSS studies. Sometimes cooler plasma "fingers" within Earth's magnetosphere extend outward towards this boundary. The interaction of these two plasmas manifests as throat aurora, with radial spokes uniquely aligned along the north-south longitudinal axis."

Observational properties of a newly discovered auroral form near local noon, called throat aurora, revealing combined contributions for its generation from inside and outside of the magnetosphere. The image gives a schematic summarizing the physical process leading to the formation of throat aurora. From Han et al. [pp. 1853–1870, doi: 10.1002/2016JA023394 ]. Image credit: E. Masongsong, H. Hietala (UCLA EPSS), D.-S. Han (Polar Research Institute of China).


J. Geophysics Research - Space Physics, Volume 122, Issue 2, February 2017, Pages 1429–2733.

March 9, 2017:

ARTEMIS measurements of magnetic reconnection jets:

Every day, invisible magnetic explosions are happening around Earth, on the surface of the sun and across the universe. These explosions, known as magnetic reconnection, occur when magnetic field lines cross, releasing stored magnetic energy. Such explosions are a key way that clouds of charged particles -- plasmas -- are accelerated throughout the universe. In Earth's magnetosphere -- the giant magnetic bubble surrounding our planet -- these magnetic reconnections can fling charged particles toward Earth, triggering auroras.

Cartoon depiction of the magnetosphere viewed from the side, with the small blue circle as Earth on the left, with the magnetotail and site of reconnection on the right. Area inset is animated in the next figure. Credit. H. Hietala, UCLA

Magnetic reconnection, in addition to pushing around clouds of plasma, converts some magnetic energy into heat, which has an effect on just how much energy is left over to move the particles through space. A recent study used observations of magnetic reconnection from NASA's ARTEMIS -- Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun -- to show that in the long tail of the nighttime magnetosphere, extending away from Earth and the sun, most of the energy is converted into heat. This means that the exhaust flows -- the jets of particles released by reconnection -- have less energy available to accelerate charged particles than previously thought.

When magnetic reconnection occurs between two clouds of plasma that have the same density, the exhaust flow is wildly unstable -- flapping about like a garden hose with too much water pressure. However, the new results find that, in the event observed, if the plasmas have different densities, the exhaust is stable and will eject a constant, smooth jet. These differences in density are caused by the interplay of the solar wind -- the constant stream of charged particles from the sun -- and the interplanetary magnetic field that stretches across the solar system.

Magnetotail inset from previous figure with Earth on the left and ARTEMIS probes on the right. ARTEMIS witnessed stable exhaust flows of plasma, or reconnection jets, flowing towards Earth. The jets also accelerate plasma in the opposite direction down the magnetotail. Credit: NASA GSFC, Y.-H. Liu

These new results are key to understanding how magnetic reconnection can send particles zooming toward Earth, where they can initiate auroras and cause space weather. Such information also provides fundamental information about what drives movement in space throughout the universe, far beyond the near-Earth space we can observe more easily. The ARTEMIS spacecraft are working in tandem with other missions like Time History of Events and Macroscale Interactions during Substorms, and Magnetospheric Multiscale to form a complete picture of magnetic reconnection near Earth.

NASA Press Release

Hietala, H., A. V. Artemyev, and V. Angelopoulos (2017), Ion dynamics in magnetotail reconnection in the presence of density asymmetry, J. Geophys. Res. Space Physics, 122, doi:10.1002/2016JA023651.

January 17, 2017:

2016 Fall AGU Outstanding Student Paper Award Winner

EPSS graduate student Terry Liu has been awarded an outstanding student paper award at the 2016 Fall AGU meeting based on his presentation and paper titled "Observations of a new foreshock region upstream of a foreshock bubble’s shock." Congratulations, Terry!

June 20, 2016:

THEMIS study featured on cover of GRL and received GEM Outstanding Student Poster Award:

UCLA PhD student Terry Z. Liu used THEMIS data from 2008 to profile the turbulent solar wind plasma upstream of the magnetosphere. Since the solar wind is moving at supersonic speeds, when it encounters the magnetopause, a collisionless shockwave forms. Some reflected ions can be energized to form a "foreshock bubble," which Terry found can in turn form its own foreshock. The two THEMIS probes happened to be in just the right place and time to witness the bubble and the reflected ions in close succession, helping to reveal the complex geometry of the plasma interactions. Way to go Terry!

A foreshock bubble's shock, GRL Cover image. Credit: Emmanuel Masongsong and Heli Hietala, UCLA; NASA EYES.

The image above is an artist's representation of a baby foreshock emerging from its parent foreshock. Incoming solar wind ion beams (blue arrows) get reflected (spiral purple arrows) at Earth's bow shock (red, far right). These reflected ions form Earth’s parent foreshock (faint orange glow) and gradually become diffuse (blurred spiral purple arrows). In this study, a solar wind discontinuity was observed by the THEMIS-B spacecraft (far left), causing some of the reflected foreshock ions to become trapped and thermalized (center, purple arrows bending to become yellow arrows in random directions). These hot ions expand and form a foreshock bubble with a hot core (yellow) and its own shock (red) due to fast expansion. The THEMIS-C spacecraft (center) observed that this new shock can also reflect solar wind ion beams (blue arrows) and form a baby foreshock (spiral purple arrows with orange glow).

For more specific details, please refer to the THEMIS Science Nugget Summary here.

Liu, T. Z., H. Hietala, V. Angelopoulos, and D. L. Turner (2016), Observations of a new foreshock region upstream of a foreshock bubble's shock, Geophys. Res. Lett., 43, 4708–4715, doi:10.1002/2016GL068984.

February 25, 2016:

THEMIS featured in The Guardian, for new popular book on the aurora:

Featured in The Guardian: author and plasma physicist Dr. Melanie Windridge intertwines the cultural and scientific history of the aurora, and shares THEMIS mission breakthroughs in her new book, "Aurora: In Search of the Northern Lights​​​​​." Dr. Windridge reveals the rich history and enduring mysteries of the northern lights, from the ancient folklore of Arctic peoples to her own polar research adventures, elaborating on the latest findings about space weather and the complex mechanisms of the aurora. She also discusses the story behind the THEMIS mission, and the groundbreaking science fostered by its expansive array of All-Sky Imagers and magnetometers across the northern hemisphere, which continue to help researchers piece together critical elements of the auroral puzzle.

Credit: Harper Collins

"Canada has a vast amount of land underneath the auroral oval, so imaging the northern lights is an important research activity. This composite image from several cameras looking directly upwards shows how a twisted band of aurora can stretch all across the American continent. But it’s not simply pretty. Our atmosphere is the screen where the drama of the magnetosphere plays out. By studying the aurora we can learn about the processes happening far out in space." -M. Windridge

Mosaic of the aurora from the THEMIS All-sky imagers. Credit: NASA GSFC/SVS

The Northern Lights Illuminated - in Pictures, featured on

The book was published by Harper Collins, more details can be found on the author's website.

January 15, 2015:

JGR Editor's Highlight, ARTEMIS 3D Lunar Wake Observations:

The twin ARTEMIS spacecraft are revealing new aspects of the solar wind's interaction with Earth’s moon. The lunar wake extends a long distance (>12 lunar radii), and its void distorts the interplanetary magnetic field causing it to bulge moonward. High energy-particles are able to refill the wake, increasing the temperature in the areas of lowest density, indicated in red."
Credit: E. Masongsong UCLA EPSS/IGPP, NASA EYES.

Unlike the Earth, whose magnetic field deflects much of the incoming solar wind, the surface of the Moon absorbs most of the particles that the Sun sends its way. This creates a void behind the moon that gradually refills with plasma, forming a cone-shaped "lunar wake." However, the processes that govern refilling remain unclear, although models suggest they probably include a mixture of kinetic effects and effects particular to the dynamics of electrically conducting fluids.

Univ. of Alaska's Hui Zhang and UCLA colleagues now provide a detailed characterization of the lunar wake and its relationship to the direction and strength of the solar wind. The researchers used two years' worth of data from the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission to characterize many physical properties of the wake, including its magnetic properties, ion and electron densities, temperatures, pressures, and flow, while simultaneously monitoring the solar wind.

The scientists find that the lunar wake trails behind the Moon out to a distance at least 12 times its radius. The edges of the wake generate density waves that form disturbances that propagate both outward and inward like the wake of a boat. This process can mostly be explained by known principles about the flow of plasma. In contrast, they find that kinetic effects most likely explain the mid-wake maximum in ion and electron temperatures, which may result from high-energy particles refilling the wake faster than their low-energy counterparts.

Notably, the researchers find that the angle between the direction of the solar wind and the orientation of the interplanetary magnetic field also influence the shape and character of the lunar wake, making it more ring-like for angles close to parallel and flatter for more perpendicular configurations. The scientists also find that the interplanetary magnetic field itself bulges toward the Moon inside the lunar wake, although they can’t yet identify the mechanism behind this observation.

Wendel, J. (2014), Satellite data yields detailed picture of the lunar wake, Eos. Trans. AGU, in press.

Zhang, H., K. K. Khurana, M. G. Kivelson, V. Angelopoulos, W. X. Wan, L. B. Liu, Q.-G. Zong, Z. Y. Pu, Q. Q. Shi, and W. L. Liu (2014), Three-dimensional lunar wake reconstructed from ARTEMIS data, J. Geophys. Res. Space Physics, 119, 5220–5243, doi:10.1002/2014JA020111.

Aug. 7, 2014:

ELFIN Cubesat Mission is Funded! Undergraduates to Build First Satellite at UCLA

The Electron Loss and Fields Investigation CubeSat, or ELFIN, is a tiny satellite the size of a loaf of bread that still packs the scientific punch of significantly larger, more expensive satellites. When launched, ELFIN will determine how solar wind particles and radiation behave in Earth's environment, a topic of increasing concern because magnetic storms can wreak havoc on space infrastructure like GPS, communication and weather satellites, and even damage the electrical grid here on Earth.

From the beginning, ELFIN had only scant internal funding, and the outlook for completion was unclear. In spite of this uncertainty, a team of several dozen intrepid undergraduate students took on the project as their own, collectively putting in thousands of hours as a labor of love, developing and testing the satellite's subsystems with the hope that the project would someday be fully funded.

After three years of diligent work and patience, the tide finally turned in 2013 when the U.S. Air Force awarded the team a $110,000 grant to continue development and buy much-needed parts. Last February, the opportunity to achieve their goal became even more real for these space Bruins when NASA's CubeSat Initiative and the Low-Cost Access to Space program guaranteed them a launch spot.

Finally on May 23, the team was awarded $1.2 million jointly from NASA and the National Science Foundation, ensuring enough funding to put the space-qualified hardware in orbit and to operate it for six months from the UCLA Mission Operations Center, to be located on campus.

A collaboration between the Aerospace Corporation and UCLA's departments of Earth, Planetary and Space Sciences; Mechanical and Aerospace Engineering (MAE); and Atmospheric and Oceanic Sciences, ELFIN will not only benefit UCLA students, who will have the opportunity to work on a real-world space program, but will also resolve a critical space physics question.

"The ELFIN experience is unusual in comparison to an industry that typically deals with one-ton satellites that take up to 10 years to build by a veritable army of engineers," Turner said. "This will be an invaluable, once-in-a-lifetime opportunity for our students — a ride to space they will never forget!"

The satellite is tentatively scheduled for launch in late 2016 or early 2017 as a secondary payload (similar to carpooling), which greatly reduces the cost of reaching space. From its polar orbit approximately 370 miles overhead, ELFIN will determine how high-energy electrons in Earth's radiation belt (located roughly 25,000 miles above the equator) are scattered out of their cyclical orbits by naturally occurring ultra-low-frequency electromagnetic waves.

These electrons are guided along Earth's magnetic field (which resembles a bar magnet) and fall into the atmosphere above the north and south poles, where their energy is transformed into the dazzling lights of the auroras. By analyzing the speed and direction of the falling electrons, the team will be able to tell what types of waves scattered them from the heart of the radiation belts. A sensitive on-board magnetometer will also look for the signature of these waves to confirm the scattering theory. Understanding this "emptying" of the radiation belts will help scientists predict the effects of future space weather storms.

"We are fortunate to be at UCLA in an environment with extremely competent staff, researchers and faculty who care and take the time to work one-on-one with us," said Chris Shaffer, a senior in MAE and ELFIN's student project manager. "We are building a team of students and staff with the mentality that there is nothing that we can't do. That teamwork will be the hallmark of our project's success. A banner stating that "Failure is not an option' has been hanging in our lab ever since we started."

Press Release - UCLA undergrads are first to build an entire satellite on campus

Daily Bruin - Forecast From Space: Satellite built by student team may help predict magnetic storms

May 1, 2014:

THEMIS research featured in Journal of Geophysics Research:

The recent paper by UCLA researcher Christine Gabrielse et al., "Statistical characteristics of particle injections throughout the equatorial magnetotail" was selected as an Editor's Highlight by JGR, Space Physics.

(a) AL index. (b) Energy flux. (c) Energy flux (line spectra). Note that the ESA instrument goes near background levels around 02:00, 03:00, and 06:30 UT, explaining the behavior of the fitted channel between the ESA and SST instruments (26 keV). To avoid incorrectly selecting an injection from the fitted channel, we required that the energy flux at 26 keV be higher than that at 31 keV for selection. (d) Percent change in energy flux per minute [((Δj/j)/Δt)˙100] for each individual energy channel. Colors represent energy channels and correlate with the colors in the line spectra. Three consecutive energy channels must have a (Δj/j)/Δt that rises above the horizontal line at 25% for an injection to be selected. (e) Magnetic field in GSM coordinates. Increasing dipolarization is observed as each dipolarized flux bundle comes in, causing flux pileup around 04:00 UT. (f) Velocity in GSM coordinates. Flow reversals may represent vortices in the incoming flow and/or rebound in the flux pileup region. (g) Electric field in GSM coordinates calculated from −V × B.
Gabrielse et al., Figure 1: Seven electron injection events selected using specific criteria. Events 1 and 2: Dispersionless injections. Events 3–7: Dispersed injections.

Understanding the behavior of charged particles in the magnetotail

When the Sun spews charged particles toward the Earth, they can enter the magnetosphere and become energized as they move closer to the Earth’s surface. These energetic particles can induce the bright colors of auroras, disrupt navigational satellites, and even distort terrestrial telecommunications.

Previous research has found that the energization and transport of these particles—a process known as “particle injection”—may be correlated with the emergence of narrow, fast-flowing channels of plasma within the magnetosphere that travel earthward after energy is released in the Earth’s magnetotail. Curious about how far out these particle injections can be detected in the magnetotail, and whether or not they are actually caused by these narrow, fast-flowing bursts of plasma, Gabrielse et al. studied data from NASA's THEMIS mission, which observes large-scale space weather events beyond the orbits of geosynchronous satellites.

The authors found that energetic particle injections could, in fact, be seen approaching Earth well beyond the previously recorded distance of 6.6-12 Earth radii, even up to 30 Earth radii away and possible further. They also showed statistically that these particle injections are indeed related to the narrow channels of fast-flowing plasma, where particles are energized by the flow channels’ electric fields. Understanding how these particle injections behave at points within the radiation belts to distances greater than 30 Earth radii away will help scientists develop better forecasts of potentially damaging space weather events.

JGR Editor's Highlight: Understanding the behavior of charged particles in the magnetotail

Gabrielse, C., V. Angelopoulos, A. Runov, and D. L. Turner (2014), Statistical characteristics of particle injections throughout the equatorial magnetotail, J. Geophys. Res. Space Physics, 119, 2512–2535, doi:10.1002/2013JA019638.

Feb. 14, 2014:

THEMIS-ARTEMIS-ELFIN Bring Space Plasma to Local Elementary School

The THEMIS/ARTEMIS and ELFIN spacecraft teams spent their Valentine's Day spreading the love for space science at the local Nora Sterry Elementary School. As part of the school's Science, Literacy, and Math event (SLAM), outreach coordinator Emmanuel Masongsong and undergrads Kyle Colton and Stephen Sundin shared their awesome magnetism and space weather demonstrations, eliciting "oohs" and "aahs" from students ages 3-8 and their parents.

The young ones were delighted with live pictures of the sun, liquid magnetism (ferrofluid), a handheld "mini THEMIS" probe, and the recently constructed Planeterrella plasma generator. Kyle and Stephen showed some cool magnetic magic tricks (copper tube showing Lenz's law and a homopolar motor showing Lorentz force) and demonstrated the basics of satellite communication with Morse code.

Click HERE to see video of the UCLA Planeterrella in action!

The Experimental Space Physics Group is seeking K-12 educators who would be interested in magnetism and space science presentations at their schools or in their classrooms. For more information or to request a presentation, please contact

Jan. 22, 2014:

THEMIS-ARTEMIS-ELFIN meet NASA Director Charles Bolden

The extraordinary military airman, astronaut, and chief NASA administrator Charles F. Bolden paid a visit to UCLA Earth, Planetary, and Space Sciences on January 22nd, 2014. He gave an inspiring talk on his own journey through the space program and the current and future goals of NASA. He stressed the critical importance of science education in maintaining our nation's leadership in all fields of technology, including space. Aside from the lecture, he met briefly with our undergrads and grad students to hear about the latest space weather research and cubesat development in our group, and then browsed our newly opened Meteorite Museum (the largest collection on the West coast). What an amazing individual with such varied accomplishments and honorable service. Thank you for visiting!

Dec. 3, 2013:

THEMIS and ARTEMIS a Magnetic Attraction at UCLA Public Outreach Event

The NASA THEMIS and ARTEMIS missions drew an impressive crowd at the 4th annual Exploring Your Universe outreach event, held at UCLA in Los Angeles, on Nov. 17, 2013. Representing two of UCLA's active space missions, the exhibit exposed the public to "space weather," the study of the sun's activity and influence on Earth's protective magnetic shield, the magnetosphere. Visitors were intrigued by informative posters and stunning videos on the electrical connection between our sun and the planets, and had the opportunity to question real space scientists and meet student researchers-in-training.

Kids and adults ages 7-70 enjoyed multiple interactive displays: touching glowing plasma spheres, seeing Earth's and other planetary magnetic fields in 3D, comparing live pictures of the sun in different wavelengths of light, and even making their own sunspots! Although the wait in line was long, many lucky visitors witnessed the debut of a specially built display called the Planeterrella, an up-close demonstration of the solar wind and famed Northern Lights. This "aurora in a bottle" simulator was redesigned by Dr. Jean Lilensten at CNRS-IPAG in Grenoble, France, as a modernized version of the original Birkeland Terrella model built in the late 1800s to explain how the aurora are electrical in nature. The UCLA Planeterrella was especially popular because it helped visitors to actually see the sun-Earth connection in person, including solar flares, the solar wind, Van Allen radiation belts, and auroral ovals that can only be observed by satellites. It is the second educational plasma generator of its kind built in the US, after NASA's Langley Space Center.

An estimated 1000+ space weather tourists dropped by the exhibit, asked awesome questions, and shared their knowledge about electricity and magnetism in space. Most visitors had already seen photos of solar storms, but they left with a greater appreciation of the solar wind and its electrified gases, as well as the importance of understanding their effects on Earth's invisible magnetic field. "Space weather is important to study because, like weather on Earth, it is highly unpredictable and can damage critical GPS and communications satellites, harm astronauts on the space station, and worst case, cause extensive blackouts on the ground," explained undergraduate engineering student Gautam Suri, who built the Planeterrella with graduate student Mac Booth.

By introducing the public to the sun-Earth connection and connecting the concepts of magnetism, electricity, and planetary science, visitors were able to grasp the importance of space weather and the satellite resources that help us predict solar and Earth-based "magnetic storms" that can threaten our modern technology. "We are fortunate to have a fleet of spacecraft observing potential hazards in near-Earth space," said UCLA outreach educator Emmanuel Masongsong, "in particular the five THEMIS-ARTEMIS probes that continue to piece together the powerful electric and magnetic energy that fuels Earth's radiation belts as well as the stunning auroral lights." Most importantly, visitors young and old realized that magnets are not just cool toys or only for powering hybrid car motors and MRIs, they are a fundamental aspect of ongoing life on Earth and are key to the formation and evolution of planets, moons, and stars, extending far beyond our galaxy to other planetary systems throughout the universe!

Nov. 8, 2013:

THEMIS-MMS Conjunctions: A Step Closer to Reality:

The recent maneuver campaign for the three THEMIS probes has been completed, and recent orbit determination has confirmed the maneuvers have been 100% successful. Between Sep. 25, 2013 and Oct. 22, 2013 we have executed a total of 19 maneuvers: There were 4 orbit change maneuvers, one attitude, and one spin rate adjustment per probe, and on September 24, we had our first ever collision avoidance maneuver for P3PD with a zero net change of the orbital period.

By lowering perigee and apogee altitudes we further increased our orbital drift. This final step in our preparation for the upcoming conjunctions with MMS in 2016 and 2017, originally planned for July, was delayed multiple times until early MMS thermal vacuum test results confirmed there are no major hurtles towards an MMS launch in late 2014. By doing so we traded as much as possible of our valuable drift time against the ability to account for a possible major launch delay of MMS into spring 2015 (which would have required imparting a drift in the reverse direction). Despite the recent MMS launch delay by one month there is still room for adjustments to preserve good quality lineups. We are therefore optimistic that we can still take full advantage of this very unique opportunity of THM-MMS conjunctions.

For the near term cooperation with the Van Allen Probes we increased the probe separation to about 7.5h. This nearly equal spread along the orbit was achieved through specific relative timing of the MMS-lineup maneuvers. And as you may have noticed, FS intervals have increased in duration to more typical 18-20hrs recently, thanks to the use of the White Sands antenna (thank you NASA).

All probes are in a clean spin rate window (low interference with FGM) and the attitudes have been optimized for the tail season in 2014 (sunward spin axis tilt) when we plan to return to smaller separations to obtain a second batch of 1-2Re inter-probe separation data. For the long term, THEMIS is on its way to be in the magnetotail during winter of 2016 and 2017 while again in conjunction with the GBOs! This will be an amazing opportunity to conduct Heliophysics System Observatory magnetotail studies.

Soon, there will be an update at SPDF, projecting the near and long term plans of THEMIS based on the post maneuver states. The current data at SPDF reflect the older long term plans based on only earlier maneuvers (from July), but will be updated soon. By having MMS orbits at SPDF as well, we plan to seek community feedback on how to best optimize the tetrahedral configuration of THEMIS around MMS.

We would like to use this opportunity to thank all of you who supported these maneuvers and in particular the flight dynamics, scheduling, and operation teams. We are confident that science will be well served with the outcome of all their hard work and that NASA will get the confirmation that their further support for THEMIS was worth their funding.

September 27, 2013:

ARTEMIS unravels energy conversion at reconnection fronts:

The twin ARTEMIS probes' lunar vantage point was key to unraveling energy conversion in Earth's magnetosphere, as reported in the recent journal Science. With an unprecedented alignment of 8 spacecraft including THEMIS, Geotail and GOES, researchers from UCLA, JAXA, and Austrian IWF observed reconection fronts moving towards Earth and away beyond the moon.

Solar storms — powerful eruptions of solar material and magnetic fields into interplanetary space — can cause what is known as "space weather" near Earth, resulting in hazards that range from interference with communications systems and GPS errors to extensive power blackouts and the complete failure of critical satellites.

New research published today increases our understanding of Earth's space environment and how space weather develops.

Some of the energy emitted by the sun during solar storms is temporarily stored in Earth's stretched and compressed magnetic field. Eventually, that solar energy is explosively released, powering Earth's radiation belts and lighting up the polar skies with brilliant auroras. And while it is possible to observe solar storms from afar with cameras, the invisible process that unleashes the stored magnetic energy near Earth had defied observation for decades.

In the Sept. 27 issue of the journal Science, researchers from the UCLA College of Letters and Science, the Austrian Space Research Institute (IWF Graz) and the Japan Aerospace Exploration Agency (JAXA) report that they finally have measured the release of this magnetic energy close up using an unprecedented alignment of six Earth-orbiting spacecraft and NASA's first dual lunar orbiter mission, ARTEMIS.

Space weather begins to develop inside Earth's magnetosphere, the giant magnetic bubble that shields the planet from the supersonic flow of magnetized gas emitted by the sun. During solar storms, some solar energy enters the magnetosphere, stretching the bubble out into a long, teardrop-shaped tail that extends more than a million miles into space.The stored magnetic energy is then released by a process called "magnetic reconnection." This event can be detected only when fast flows of energized particles pass by a spacecraft positioned at exactly the right place at the right time. Luckily, this happened in 2008, when NASA's five Earth-orbiting THEMIS satellites discovered that magnetic reconnection was the trigger for near-Earth substorms, the fundamental building blocks of space weather. However, there was still a piece of the space weather puzzle missing: There did not appear to be enough energy in the reconnection flows to account for the total amount of energy released for typical substorms.

In 2011, in an attempt to survey a wider area of the Earth's magnetosphere, the THEMIS team repositioned two of its five spacecraft into lunar orbits, creating a new mission dubbed ARTEMIS after the Greek goddess of the hunt and the moon. From afar, these two spacecraft provided a unique global perspective of energy storage and release near Earth.

Similar to a pebble creating expanding ripples in a pond, magnetic reconnection generates expanding fronts of electricity, converting the stored magnetic energy into particle energy. Previous spacecraft observations could detect these energy-converting reconnection fronts for a split second as the fronts went by, but they could not assess the fronts' global effects because data were collected at only a single point. By the summer of 2012, however, an alignment among THEMIS, ARTEMIS, the Japanese Space Agency's Geotail satellite and the U.S. National Oceanic and Atmospheric Administration's GOES satellite was finally able to capture data accounting for the total amount of energy that drives space weather near Earth. During this event, reported in the current Science paper, a tremendous amount of energy was released.

The amount of power converted was comparable to the electric power generation from all power plants on Earth — and it went on for over 30 minutes. The amount of energy released was equivalent to a 7.1 Richter-scale earthquake. Trying to understand how gigantic explosions on the sun can have effects near Earth involves tracking energy from the original solar event all the way to Earth. It is like keeping tabs on a character in a play who undergoes many costume changes, researchers say, because the energy changes frequently along its journey: Magnetic energy causes solar eruptions that lead to flow energy as particles hurtle away, or to thermal energy as the particles heat up. Near Earth, that energy can go through all the various changes in form once again. Understanding the details of each step in the process is crucial for scientists to achieve their goal of someday predicting the onset and intensity of space weather.

Visualization of reconnection fronts, courtesy. J. Raeder/UNH

UCLA Press Release - Lunar orbiters discover source of space weather near Earth

NASA Press Release - Several NASA Spacecraft Track Energy Through Space

Featured extensively in international media, including:, NBC News, Yahoo News, Science Magazine News, Science Daily,,, EurekAlert (AAAS), Environmental News Network, Red Orbit, Times of India, French Tribune, Le Scienze (Italy), and Newspoint Africa

Sept. 22, 2013:

Third radiation belt formation:

(Click here for animation of third belt)

Congratulations to Yuri Shprits and colleagues for explaining the mechanism of creation of the remnant belt, a 3rd radiation belt in Earth's magnetosphere using a combination of THEMIS, Van Allen probes data and modeling. The results, which appear on the Sep. 22 (2013) issue of Nature Phys. go a long way towards revealing the separate physical processes that affect different electron belts, including wave scattering, and the effects of cold plasmaspheric plasma.

Since the discovery of the Van Allen radiation belts in 1958, space scientists have believed these belts encircling the Earth consist of two doughnut-shaped rings of highly charged particles — an inner ring of high-energy electrons and energetic positive ions and an outer ring of high-energy electrons.

In February of this year, a team of Van Allen Probes scientists reported the surprising discovery of a previously unknown third radiation ring — a narrow one that briefly appeared between the inner and outer rings in September 2012 and persisted for a month (Baker et al., Science, Feb. 2013).

The above Van Allen Probe 2013 results confirmed earlier observations by THEMIS researchers (Turner et al., Nature Physics, Jan. 2012), showing the rapid loss of outer belt electrons through the magnetopause, creating a distinct "remnant" belt. The remnant belt has a lifetime of hours to days for low energy (<2MeV) particles, that is dictated by the particle losses due to various plasma waves (hiss or electromagnetic ion cyclotron – EMIC - waves). However, an equatorial >2MeV population, was present in the Van Allen Probe 2013 study event for many weeks. The new modeling results by Shprits et al., show what causes the stability of the equatorial >2MeV electrons: it is the presence of the plasmasphere that protects these particles from EMIC waves, and the lack of resonance of these particles with hiss waves inside the plasmasphere.

"In the past, scientists thought that all the electrons in the radiation belts around the Earth obeyed the same physics," said Yuri Shprits, a research geophysicist with the UCLA Department of Earth and Space Sciences. "We are finding now that radiation belts consist of different populations that are driven by very different physical processes."


Nature Physics:

March 28, 2013:

THEMIS/ARTEMIS International Team Sees Auroras:

The Spring THEMIS-ARTEMIS Science Working Group meeting brought researchers together from all over the world to share the latest findings on the magnetosphere, solar wind, and the moon. Even better, attendees were rewarded with a substorm and brilliant auroras on the closing night! The truly diverse group of 50+ space and atmospheric physics scientists represented 7 countries and 24 different institutions, all coming together to share the latest findings in the near-Earth plasma environment. The meeting discussions were inspiring and productive, though the greatest thrill was during a visit to the Poker Flat Research Range just north of Fairbanks. Even after decades of studying space physics, this was the first opportunity for many to witness the auroras' dazzling beauty in person.

At this state of the art facility, researchers stayed warm indoors (outside temp was -20F!) while patiently monitoring real-time solar wind measurements and ultra-sensitive CCD cameras displays. Periodically they would jump with excitement and a whir of outer garments as the early signs of a substorm appeared. Many were awestruck at their first sighting, and remarked on the surprising speed with which the green arcs consumed the sky. Many thanks to meeting organizer Dr. Hui Zhang and Dr. Don Hampton of University of Alaska for the Poker Flat tour, and to all attendees for their continuing contributions to THEMIS/ARTEMIS!!

(click thumbnails to enlarge)

February 19, 2013:

THEMIS 6th Year Anniversary (continued from home page):

Six Years in Space for THEMIS: Understanding the Magnetosphere Better Than Ever

Still going strong after 6 years in orbit, THEMIS continues to reveal the complexities of our magnetosphere in unprecedented detail. Read the official NASA 6th anniversary press release here:

NASA News:

Congrats to the THEMIS/ARTEMIS team and cheers to another year of exciting discoveries!

February 14, 2013:

THEMIS featured in AGU Geophysical Monograph:

A new AGU Monograph on auroral physics was recently published, prominently featuring THEMIS data. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the different planets, there are also striking differences that test our basic understanding of auroral processes. The objective, upon which this monograph is focused, is to connect our knowledge of auroral morphology to the physical processes in the magnetosphere that power and structure discrete and diffuse auroras. The volume synthesizes five major areas: auroral phenomenology, aurora and ionospheric electrodynamics, discrete auroral acceleration, aurora and magnetospheric dynamics, and comparative planetary aurora. Covering the recent advances in observations, simulation, and theory, this book will serve a broad community of scientists, including graduate students, studying auroras at Mars, Earth, Saturn, and Jupiter.

Many spacecraft missions have probed the outer magnetosphere of Earth in conjunction with ground-based and space-borne imagers, and these have contributed enormously to our understanding of the coupled magnetotail-ionosphere system. It must also be said that the THEMIS project has given a new boost to the ongoing auroral investigations, and thus it is features prominently in this volume.

Citation: Keiling, A., E. Donovan, F. Bagenal, and T. Karlsson (Eds.) (2012), Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets, Geophys. Monogr. Ser., vol. 197, 443 pp., AGU, Washington, D. C., doi:10.1029/GM197.

October 6, 2012:

THEMIS Research Highlight:

X-Y locations of the spacecraft observing the flow bursts for two data sets. Thick curve shows the GEO distance (6.6 Re). (a) Geotail locations in the events accompanied by GEO injections (red points) and in those without GEO injections (blue points). (b) Same as Figure 2a but for THEMIS spacecraft; events with simultaneous observations at two or three spacecraft are connected by line segments. Credit: V. Sergeev, St. Peterburg University

Congratulations to our colleague Victor Sergeev of St. Petersburg University! The editors of the Journal of Geophysical Research - Space Physics have selected his recent paper, entitled "Energetic particle injections to geostationary orbit: Relationship to flow bursts and magnetospheric state," as a JGR Editor's Highlight. It will also be featured as a "Research Spotlight" in Eos, AGU's weekly newspaper, to be published soon.

Most high-energy particle injections do not reach geostationary orbit

The injection of high-energy particles into the inner magnetotail is often considered a reliable sign of a magnetic substorm. These injections are often thought to be caused by flow bursts, short-lived periods of narrow fast flow streams in the magnetotail. Analyzing records of flow bursts at the entry to the night-side inner magnetosphere, from 8 to 13 Earth radii, as seen by Geotail from 1995 to 2005, and by the Time History of Events and Macroscale Interactions During Substorms (THEMIS) satellite from 2008 to 2009, Sergeev et al. (2012) found that most flow bursts do not cause the injection of high-energy particles to geostationary altitudes, and thus such injections are a poor measure of substorm activity. The authors identified 61 flow bursts using the Geotail records, and 44 using THEMIS observations. To determine whether an injection occurred with each of the flow bursts, they compared the Geotail records with publicly accessible pre-2008 particle injection data from Los Alamos National Laboratory (LANL) satellites, and turned to LANL scientists who had access to classified LANL satellite observations to confirm whether or not an injection occurred with each of the flow bursts in the THEMIS observations. The authors found that only 23 of the 61 Geotail bursts and 16 of the 44 THEMIS bursts were associated with the injection of high-energy particles into geostationary Earth orbit. The authors found that for a particle injection to make it to geostationary altitudes, the entropy parameter in the flow burst plasma needed to be comparable to the entropy at geostationary Earth orbit. The authors found that a strong solar wind driving, and high plasma pressure, at geostationary orbit could help drive up geostationary entropy and allow the injection of accelerated flow burst plasma.

Citation: Sergeev, V. A., I. A. Chernyaev, S. V. Dubyagin, Y. Miyashita, V. Angelopoulos, P. D. Boakes, R. Nakamura, and M. G. Henderson (2012), Energetic particle injections to geostationary orbit: Relationship to flow bursts and magnetospheric state, J. Geophys. Res., 117, A10207, doi:10.1029/2012JA017773.

September 19, 2012:

UCLA THEMIS Research Highlight:

The editors of the journal Geophysical Research Letters have selected Lunjin Chen's recent paper, entitled "Modulation of plasmaspheric hiss intensity by thermal plasma density structure," as both a GRL Editor's Highlight and a feature in the "Research Spotlight" section on the back page of Eos, AGU's weekly newspaper.

Plasmaspheric hiss amplification mechanisms identified (by Colin Schultz, from Eos)

A representative chorus ray that is guided by a density crest. The magenta line represents the ray path, along which wave normal directions are denoted by the short segments color-coded by the propagation time (up to 17 seconds). The model plasma density is shown in the background in gray scale.

Over the past 3 decades the hypothesis that chorus waves- a form of highintensity plasma wave often found in the outer magnetosphere- evolve into plasmaspheric hiss in the plasmasphere has grown in prominence. Plasmaspheric hiss is a form of low-frequency radio wave that is often observed in the regions within the plasmasphere that have high plasma densities. Plasmaspheric hiss is important in that the hiss waves interact with highenergy electrons in Earth's geomagnetic field, carving out a swath between the inner and outer Van Allen radiation belts to form the "slot region," a relative safe zone with minimized radiation hazard. Though modeled simulations of plasmaspheric hiss formation from chorus waves have been able to reproduce the major properties of observed hiss, they often underestimate hiss intensity by 10-20 decibels. Drawing on observations from the planet's dayside made using NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite, Chen et al. examine two mechanisms that could make up for this shortfall.

Citation: Chen, L., R. M. Thorne, W. Li, J. Bortnik, D. Turner, and V. Angelopoulos (2012), Modulation of plasmaspheric hiss intensity by thermal plasma density structure, Geophys. Res. Lett., 39, L14103, doi:10.1029/2012GL052308.

June 26, 2012:

Jenni Kissinger's paper highlighted by JGR and Eos:

The editors of the Journal of Geophysical Research - Space Physics have selected Jenni Kissinger's recent paper, entitled "Diversion of plasma due to high pressure in the inner magnetosphere during steady magnetospheric convection," as both a JGR Editor's Highlight and a feature in the "Research Spotlight" section on the back page of Eos, AGU's weekly newspaper.

Steady convection keeps Earth's magnetic field in balance (by Colin Schultz, from Eos)

Contour maps of average Earthward magnetic flux transport in the X-Y GSM plane by type of activity: (top) quiet, pre-SMC, and SMC and (bottom) substorm growth, expansion, and recovery. All plots are to the same color scale.

The onslaught of the solar wind on the Sun-facing side of Earth's magnetic field causes terrestrial magnetic field lines to break through magnetic reconnection. The persistent pressure of the solar wind pulls the field lines and the associated plasma around to the magnetotail on Earth's nightside, where magnetic reconnection occurs once again to form the plasma sheet region. This uneven distribution creates a pressure gradient that drives nightside plasma back toward the planet. The Earthward transport of this nightside magnetospheric plasma is known to occur in one of two ways: as a magnetic substorm or as steady magnetospheric convection (SMC). Substorms include acute inflows that cause plasma to pile up in the inner magnetosphere and have been tied to the onset of aurorae. SMC, on the other hand, has been proposed as a mechanism for rebalancing the plasma gradient established between the day and night sides of Earth's magnetic field. Kissinger et al. compiled 14 years of magnetic field and plasma observations to study how plasma flows and magnetospheric conditions differ between SMC events and substorms.

Citation: Kissinger, J., R. L. McPherron, T.-S. Hsu, and V. Angelopoulos (2012), Diversion of plasma due to high pressure in the inner magnetosphere during steady magnetospheric convection, J. Geophys. Res., 117, A05206, doi:10.1029/2012JA017579.

May 3, 2012:

THEMIS/ARTEMIS UCLA Students Receive AGU Outstanding Student Paper Award:

Two of our graduate students, Michael Hartinger and Jennifer Kissinger, each received an Outstanding Student Paper Award for their presentations at the 2011 American Geophysical Union Fall Meeting in San Francisco, CA. Congratulations to both of them on a job well done!

"Observations of a cavity mode outside the plasmasphere by THEMIS" by Michael Hartinger (abstract)

"Is a Substorm Expansion Required to Initiate a Steady Magnetospheric Convection Event?" by Jennifer Kissinger (abstract)

Magnetosphere simulation with THEMIS spacecraft conjuction in the equatorial plane.
Credit: J. Raeder (UNH), NASA/Goddard Scientific Visualization Studio.

May 1, 2012:

THEMIS/ARTEMIS featured on Geophysical Research Letters Cover

A THEMIS/ARTEMIS mission spacecraft (P1) and Jimmy Raeder's simulation rendition of a THEMIS major conjunction are prominently featured on the cover of today's (March 16, 2012, Vol. 39, No. 5) issue of Geophysical Research Letters.This happened thanks to the review paper on substorm research by Victor Sergeev and colleagues which is published in this same issue.

Congratulations to Victor on his paper and to the THEMIS/ARTEMIS communities for continuing the great pace of discoveries on substorms and so many other topics spanning the entire magnetosphere (and which are increasingly including the storms of the current solar cycle!).

Link to journal:
Cover image: JPG - PDF

Source: Sergeev, V. A., V. Angelopoulos, and R. Nakamura (2012), Recent advances in understanding substorm dynamics, Geophys. Res. Lett., 39, L05101, doi:10.1029/2012GL050859.

From October to December 2003, the radiation belts swelled and shrank in response to geomagnetic storms as particles entered and escaped the belts. Credit: NASA/Goddard Scientific Visualization Studio

January 29, 2012:

THEMIS research published in Nature Physics Journal:

Congratulations to Drew Turner for his Nature Physics publication on: "Explaining sudden losses of outer radiation belt electrons during geomagnetic storms" published on-line on January 29 and making the news around the world!

Using combined data from THEMIS, GOES, and NOAA-POES satellites, Dr. Turner's research explains how electron losses through the magnetopause resolve a long standing mystery of electron drop-outs during storm main phase.

Read the article here.

NASA press release here.

Source: Turner, D. L., Y. Shprits, M. Hartinger, V. Angelopoulos (2012), Explaining sudden losses of outer radiation belt electrons during geomagnetic storms, Nature Phys., doi:10.1038/nphys2185.