News & Events


February 27, 2019:

ARTEMIS mission reveals origins of moon's "sunburn" (continued from home page):

Every object, planet or person traveling through space has to contend with the Sun's damaging radiation — and the Moon has the scars to prove it. Research using data from NASA's ARTEMIS mission — short for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun — suggests how the solar wind and the Moon's crustal magnetic fields work together to give the Moon a distinctive pattern of darker and lighter swirls.

Research using data from NASA's ARTEMIS mission suggests how the solar wind and the Moon's crustal magnetic fields work together to give the Moon a distinctive pattern of darker and lighter swirls. Credits: NASA's Goddard Space Flight Center

The Sun releases a continuous outflow of particles and radiation called the solar wind. The solar wind washes over the planets, moons and other bodies in our solar system, filling a bubble of space — called the heliosphere — that extends far past the orbit of Pluto.

Here on Earth, we're largely protected from the damaging effects of the solar wind: Because the solar wind is magnetized, Earth's natural magnetic field deflects the solar wind particles around our planet so that only a small fraction of them reach our planet's atmosphere.

But unlike Earth, the Moon has no global magnetic field. However, magnetized rocks near the lunar surface do create small, localized spots of magnetic field that extend anywhere from hundreds of yards to hundreds of miles. This is the kind of information that needs to be well understood to better protect astronauts on the Moon from the effects of radiation. The magnetic field bubbles by themselves aren’t robust enough to protect humans from that harsh radiation environment, but studying their structure could help develop techniques to protect our future explorers.

"The magnetic fields in some regions are locally acting as this magnetic sunscreen," said Andrew Poppe, a scientist at the University of California, Berkeley, who researches the Moon's crustal magnetic fields using data from NASA's ARTEMIS mission along with simulations of the Moon's magnetic environment.

Research using data from NASA's ARTEMIS mission suggests that lunar swirls, like the Reiner Gamma lunar swirl imaged here by NASA's Lunar Reconnaissance Orbiter, could be the result of solar wind interactions with the Moon's isolated pockets of magnetic field. Credits: NASA LRO WAC science team

These small bubbles of magnetic "sunscreen" can also deflect solar wind particles — but on a much smaller scale than Earth's magnetic field. While they aren’t enough to protect astronauts by themselves, they do have a fundamental effect on the Moon’s appearance. Under these miniature magnetic umbrellas, the material that makes up the Moon's surface, called regolith, is shielded from the Sun's particles. As those particles flow toward the Moon, they are deflected to the areas just around the magnetic bubbles, where chemical reactions with the regolith darken the surface. This creates the distinctive swirls of darker and lighter material that are so prominent they can be seen from Earth — one more piece of the puzzle to help us understand the neighbor NASA plans to re-visit within the next decade.


NASA Mission Reveals Origins of Moon's 'Sunburn'


Poppe, A. R., J. S. Halekas, C. Lue, and S. Fatemi (2017), ARTEMIS observations of the solar wind proton scattering function from lunar crustal magnetic anomalies, J. Geophys. Res. Planets, 122, 771–783, doi:10.1002/2017JE005313.

Poppe, A.R., S. Fatemi, I. Garrick-Bethell, D. Hemingway, M. Holstrom (2016), Solar wind interaction with the Reiner Gamma crustal magnetic anomaly: Connecting source magnetization to surface weathering, Icarus, 266, 261-66,

December 13, 2018:

ARTEMIS paper featured on JGR Space Physics website:

Three components and the total magnetic field from ARTEMIS P2 (THC) fluxgate magnetometer. The plot starts from 20:39:00 UT. The shock is at 20:39:42.45 UT at THC. Left panel: the magnetic field components Bx,By,Bz in the GSE coordinates XYZ. Right panel: the magnetic field components Bx,By,Bz in the shock coordinates XYZ. In both panels the magnetic fieldmagnitude |B| is shown by the black line.

Congratulations to Gedalin et al., whose paper "Ion Dynamics and the Shock Profile of a Low-Mach Number Shock" was featured on the JGR Space Physics website. They used ARTEMIS P2 (THC) measurements of the fluctuating magnetic field detected at low-Mach number shocks. Separation of the essential shock profile from features superimposed on it is one of the basic problems of shock physics. The study authors achieved this separation by using a combined analytical-numerical-simulative analysis. They show that the macroscopic fields of the shock play the main role in the formation of downstream ion distributions. The measured ion distributions from ARTEMIS/ESA agree well with the theoretically predicted onset of the anisotropy at the shock crossing and its persistence well into the downstream region.

The enlarged view of the shock transition with the approximate beginning and end of the ramp marked. The beginning and end of the shock ramp are defined by averages of upstream and downstream fields over the time intervals specified in the text. The arrows point to where the magnetic field is equal to these averages.


Gedalin, M., Zhou, X., Russell, C. T., Drozdov, A. Y., Liu, T. Z. (2018). Ion dynamics and the shock profile of a low‐Mach number shock. Journal of Geophysical Research: Space Physics, 123, 8913–8923.

September 18, 2018:

ARTEMIS lunar ionosphere discovery profiled in National Geographic:

Congratulations to Halekas et al., whose GRL paper titled: "A tenuous lunar ionosphere in the geomagnetic tail" was featured in National Geographic magazine. Their new study reminds us that our pale celestial guardian is more dynamic than it seems from afar. Fresh measurements of its flimsy atmosphere back up the idea that our lunar companion is surrounded by an electric shell, and that shell seems to gather power when Earth shields it from the fury of the sun during a full moon. In effect, when you gaze at a bright full moon shining in the sky, you are probably seeing the lunar orb at its most electric.

A full moon seems to brush Earth's atmosphere as seen from the International Space Station. (Credit: NASA)

The full moon lies within the elongated tail of Earth's magnetic field. This means the moon and the faint husk of the lunar ionosphere are shielded from much of the highly energetic solar wind that constantly streams into deep space. During this critical window, ARTEMIS could track the plasma waves emerging from the sunlight-bombarded lunar dayside and create a much more detailed picture of the moon's ionosphere. This was the first time such an incredibly precise technique has been used on the moon, and it revealed that the lunar ionosphere is about a million times more tenuous than Earth's.

Schematic illustration of the plasma flows, electromagnetic fields, and electric currents around the Moon in thegeomagnetic tail.

Weak though it may be, the lunar-derived plasma has appreciably higher density while in this refuge than the density of the plasma surrounding it. This suggests that the moon's ionosphere becomes more prominent when it's in Earth's protection. Halekas describes this relative ionospheric peak as "a little source of plasma bubbling and seething around the moon." Crucially, this means that the lunar plasma can measurably perturb the plasma coming from Earth and the sun, leading to observable changes in electrical currents and the distribution of electrons around the region. It's possible that there's even a plasma-based connection between Earth and the moon, and previous research offers some tentative evidence that such a particle exchange exists.

Source: Andrews, Robin G. (2018), The Moon Is Electric—Especially When It's Full, Published on Sept. 18 2018.

Citation: Halekas, J. S., Poppe, A. R., Harada, Y., Bonnell, J. W., Ergun, R. E., & McFadden, J. P. (2018). A tenuous lunar ionosphere in the geomagnetic tail. Geophysical Research Letters, 45.

July 20, 2018:

ARTEMIS observes Kelvin-Helmholtz waves in Earth's magnetic field, spotlight in Eos Magazine:

The instability that arises where there's a difference in velocity at the boundary between two fluids—like wind blowing across water—can create Kelvin-Helmholtz waves (KHWs), which look like a series of rolling breakers hitting the beach. KHWs are frequently observed along the outermost boundary of Earth's magnetic field, where they presumably help transfer energy and plasma from the solar wind into our planet's magnetosphere. Yet the conditions under which these waves form and how they evolve over time are still poorly understood.

This artist rendering shows how Kelvin-Helmholtz instability waves in Earth's magnetic tail might propagate through time and space. Credit: Quanqi Shi

To better characterize KHWs, Ling et al. used the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) and Geotail satellites to make simultaneous observations of the waves from opposite sides of Earth's magnetic tail during an instability event that occurred between 13 and 14 March 2014. They then compared their point measurements with computer simulations of the magnetosphere's response to the solar wind conditions observed during the same period of time.

The results offer evidence that KHWs develop in Earth's magnetic tail and that their wavelengths increase as they move tailward along the boundary layer, a finding that agrees with previously published simulations. The observations also suggest that vortices created by the instability develop at roughly the same time on the tail's dawn and dusk sides, although slight differences between the two sets of satellite observations prevented the researchers from completely ruling out dusk-dawn asymmetry.

In addition to providing new observational evidence for the growth of KHWs in Earth's magnetic tail, these findings provide insight into how this crucial means of interspace energy transfer evolves through both time and space. (Journal of Geophysical Research: Space Physics,, 2018)

Eos Research Spotlight: Cook, T. (2018), Measurements of Kelvin-Helmholtz waves in Earth's magnetic field, Eos, 99, Published on 20 July 2018.

Citation: Ling, Y., Shi, Q., Shen, X.‐C., Tian, A., Li, W., Tang, B., et al. (2018). Observations of Kelvin‐Helmholtz waves in the Earth's magnetotail near the lunar orbit. Journal of Geophysical Research: Space Physics, 123, 3836–3847.

March 21, 2018:

ARTEMIS data on "Magnetic-less" Magnetotail Boundary highlighted in Eos:

Most boundaries in space are governed by magnetic fields, but not far behind the Earth, where the field change across the magnetopause plays very little role in the pressure balance relationship.

ARTEMIS boundary layer crossing event in August 2012. From top to bottom: ion and electron velocity vx, electron density ne and plasma β, plasma and magnetic field pressures, and phase space density energy-time spectrogram (omnidirectional) with ion temperature and kinetic energy shown by black curves. The crossing is at x ∼−46 RE, y ∼ 33 RE.

Space physicists like to focus on regional boundaries that are magnetized. Artemyev et al. [2017] examine a boundary where magnetic fields play only a marginal role: the far-downtail magnetopause. At distances from 50 to 200 RE downtail, they find that the pressure balance is dominated by the plasma on each side of the boundary, not the magnetic field change across the boundary. This is completely different from the dayside magnetopause, which is dominated by a magnetic field discontinuity. They find that the total energies of the ion populations inside and outside the boundary are similar, suggesting thermalization is sufficient to convert streaming magnetosheath ions into hot, rarified magnetotail ions inside the boundary.

Eos Editor's Highlight: Liemohn, M., The "Magnetic-less" Magnetotail Boundary, Eos, January 2018

Citation: Artemyev A.V, V. Angelopoulos, A. Runov, C.-P. Wang, and L.M. Zelenyi [2017], Properties of the equatorial magnetotail flanks 50-200RE downtail, Journal of Geophysical Research: Space Physics, 122,

October 17, 2017:

ARTEMIS Observes Waves Growing in near-Earth Space:

Earth has its own shield, in the form of our planet's magnetic field, that protects us from the hot, charged material called "plasma" constantly being hurled at us by the sun. When this fast-moving plasma hits Earth's magnetic shield, a bow shock is formed. Just like the curve of water that bends to the side in front of a moving ship, the bow shock is where hot plasma is deflected to the side, leaving us on Earth unaffected. However, a very small portion of the plasma bounces straight back towards the sun.

Artist depiction of the solar wind plasma (yellow) interacting with the Earth's magnetosphere (purple) to form the bow shock front (light blue).

These reflected particles interact with the plasma coming from the sun and make waves. The waves get carried with the plasma towards Earth, making it through the shield where they reach the region of space near our planet.

For the first time, scientists at the University of California, Los Angeles and the Max Planck Institute for Plasma Physics in Germany have been able to see these waves grow in the region of space where they were formed. They did so using satellites that only recently moved into a prime spot for the measurement. Before 2010, a five spacecraft mission called THEMIS was orbiting Earth. In 2010, two spacecraft split off and started orbiting the Moon, and the mission was renamed ARTEMIS. When the moon passes between the Earth and sun, ARTEMIS sees the the small portion of particles that bounce back from the bow shock; these particles are responsible for generating the waves.

"The two ARTEMIS spacecraft are ideally located for this measurement," said Seth Dorfman, the lead author of the study. "Close to the bow shock, the waves can come from many places at once, but it's easier to identify the wave source out near the moon. This enables a clear measurement of the waves."

These waves are not just a curiosity – they can affect us here on Earth. When the waves run into the region of space around Earth, they can cause disturbances in Earth's magnetic field all the way to the ground. Strong disturbances or "space weather" may damage our sensitive infrastructure, such as communication satellites and power grids. Much like advances in weather forecasting let us know when to get out of the wave of a hurricane, studies of how these waves behave may help us protect our satellites and power grids from space weather damage.

Source: 59th Annual Meeting of the American Physical Society, Division of Plasma Physics, Press Release

Citation: Dorfman, H. Hietala, P. Astfalk, and V. Angelopoulos, "Growth Rate Measurement of ULF Waves in the Ion Foreshock," Geophys. Res. Let. 44 (2017).

August 21, 2017:

ARTEMIS has a front row seat for The Great American Eclipse:

Millions will be watching the Sun and the Moon on Monday, but only a small number of observers know about our two little "cheerleaders" that accompany the Moon!

THEMIS C (ARTEMIS P2) will be leading and THEMIS B (ARTEMIS P1) will be following the Moon across the solar disk. As seen from Salem, OR, THEMIS C will be passing near the center of the Sun at 13:03:40 UTC (actually about 17 min before local sunrise), and THEMIS B will be passing just below the solar disk at 21:40:50 UTC.

Here is a link to a small animation:

Video courtesy of Manfred Bester, UC Berkeley SSL.

May 31, 2017:

THEMIS and ARTEMIS highlighted in Scientia:

THEMIS, ARTEMIS and the soon to be launched cubesat ELFIN were profiled in Scientia Magazine. The special issue entitled "From Climate Change to the Cosmic Web," covers many facets of geophysical, atmospheric, and solar-terrestrial processes that affect our society. The issue also features other space weather researchers including an interview with our very own Project Scientist, David Sibeck: "It really is a great time to be a researcher in our community. Probably the biggest challenge facing researchers in our field is choosing which of the many fascinating areas to work on."

Link: Berg, N., et al., "From THEMIS to ELFIN, Exploring Near-Earth Space," Scientia 112, May 2017: 94-97.

March 9, 2017:

ARTEMIS measurements of magnetic reconnection jets featured in NASA News:

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. 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.

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

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.

July 12, 2016:

ARTEMIS observes heavy ions escaped from Earth's ionosphere, GRL highlight:

Recent ARTEMIS observations of rare, terrestrial heavy ion outflow at the moon were featured as an Editor's Highlight in the journal Geophysical Research Letters. Poppe et al. report charged particles (molecular ions. N2+, NO+, O2+) flowing down the Earth's magnetotail past the Moon. These heavy ions originate from the Earth's ionosphere during strong geomagnetic storms, and can be energized and injected into Earth's magnetosphere. The ions circulate within Earth's magnetic fields, before finding an "escape route." This escape route takes them away from the Earth and they pass by the Moon on their way out. Observations of these escaping molecular ions are relatively rare. ARTEMIS data provide an exciting opportunity to learn more about how Earth loses part of its atmosphere to space, made possible by the satellites' distant perspective around the Moon.

Artist depiction of the magnetosphere viewed from above Earth, with the sun on the left and moon on the right. The magnetosphere is compressed due to increased solar wind pressure, and the colored lines show modeled paths of ions escaping Earth's ionosphere and traveling along the magnetopause to be ultimately detected by ARTEMIS at the moon.

GRL Editor's Highlight

ARTEMIS Nugget Summary

Poppe, A. R., M.O. Fillingim, J. S. Halekas, J. Raeder, and V. Angelopoulos (2016), ARTEMIS observations of terrestrial molecular ion outflow at the Moon, Geophys. Res. Lett., 43, doi:10.1002/2016GL069715.

April 4, 2016:

ARTEMIS lunar plasma waves featured in new book:

In their new book, the editors have compiled a collection of review chapters written by leading experts on the topic of low-frequency waves in space plasmas. While in the past waves in different astrophysical plasmas have been largely treated in separate books, the unique feature of this book is that it covers waves occurring in many plasma regions of our Solar System. Organized into ten parts, each representing a specific space region, the book begins with waves at Earth's ionosphere and progresses outward to various regions of Earth's magnetosphere. Then, beyond geospace, waves in the solar wind, at the Moon, and at other planets' magnetospheres are reviewed. Finally, the book finishes with waves in the Sun's atmosphere.

THEMIS and ARTEMIS results are integral parts of many chapters, including those reviewing waves at the Moon, Earth's ionosphere and magnetosphere, and the solar wind.


Keiling, A., D.-H. Lee, V. Nakariakov (2016), Low-Frequency Waves in Space Plasmas, Geophys. Monogr. Ser., vol. 216, 528 pp., John Wiley & Sons, Inc., Hoboken, NJ.

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.

Zhang et al. 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.

April 8, 2014:

ARTEMIS and LADEE missions synergize to explain lunar dust:

Notional view of the LADEE and ARTEMIS spacecraft superimposed on Clementine star-tracker imagery from 1994 [NASA/DOD/JPL-Caltech].

ARTEMIS' contributions to the Lunar Atmosphere Dust Environment Explorer (LADEE) mission were highlighted in the recent issue of AGU's Eos journal. The feature reveals some of their preliminary results on the moon's dust and plasma environment, presented at the 45th Lunar and Planetary Science Conference in March 2014.

LADEE's primary mission to study the the distribution, sources, and sinks of lunar atmospheric dust is nearing completion, after 6 months in orbit. UCB SSL's Jasper Halekas stressed the importance of multi-spacecraft observations of the solar wind at the moon, where ARTEMIS observations of helium were used to corroborate LADEE measurements. This is the first use of dedicated space weather satellites to better understand planetary phenomena, specifically the tenuous dust at the moon that may be the most common type of atmosphere in our solar system.

With ARTEMIS data, Halekas attempted to calculate the total supply of helium at the Moon, delivered by the solar wind. He then compared this with data from LADEE and got matching results. "I submit to you that this is the best correlation you can ever get between two different spacecraft that collect two completely different kinds of measurements," Halekas said.

LADEE will conclude it's mission in the coming weeks by impacting the lunar surface, which will allow the craft to make critical low-altitude observations. Congrats to the LADEE and ARTEMIS teams for their hard work, and we look forward to their forthcoming publications explaining the phenomenon of atmospheric dust.

Kumar, M. (2014), Preliminary Results From Probe of the Moon's Dust Environment, Eos Trans. AGU, 95(14), 119.

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.

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)

May 1, 2012:

THEMIS/ARTEMIS featured on cover of Geophysical Research Letters (continued from home page):

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

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

July 18, 2011:

ARTEMIS P2 finally arrives at its new home:

On July 17th, 2011 the second probe P2 of the ARTEMIS mission successfully entered orbit around the moon after a circuitous 2-year journey from Earth orbit.

On July 17th, 2011 the second probe P2 of the ARTEMIS mission successfully entered orbit around the moon after a circuitous 2-year journey from Earth orbit. Shortly after the two probes completed their original mission studying Earth's magnetic field in 2009 (THEMIS), they were propelled using carefully designed gravity-assist maneuvers to farther and farther orbits. Due to Earth's impending unacceptably long shadows, the spacecraft took refuge in the Lagrangian points on either side of the moon. ARTEMIS P1 and P2 were the first spacecraft ever to use those complex orbits operationally.

After using the Lagrange orbits as observational outposts for 9 months, the two spacecraft were subsequently staged to enter into stable lunar orbits. The P1 probe entered lunar orbit on June 27th, 2011, and now with its twin P2 orbiting in the opposite direction around the moon, the pair's sensitive instruments will yield the first 3D measurements of the moon's magnetic field to determine its regional influence on solar wind particles.

Read more about the ARTEMIS mission here:

ARTEMIS-P2 insertion into lunar orbit on Sunday July 17, 2011. The orbit is shown in a fixed Earth-Moon frame (horizontal axis, Earth to the left), viewed from above the ecliptic. Tickmarks are one-day intervals. P2 is leaving its prior trajectory, hovering in the Lagrange point between Earth and Moon (centered at L1 in the figure) to now enter a stable lunar orbit, its final destination. The P2 thrusters will be fired during three concecutive intervals lasting about 3 hrs at the time of the lunar orbit insertion (LOI), indicated by the red trace.

Credit: NASA/Goddard Space Flight Center.

June 27, 2011:

ARTEMIS/P1 now successfully inserted into Lunar Orbit. (Continued from home page):

This morning ARTEMIS P1 (a.k.a. THEMIS B) was successfully inserted into a lunar orbit. The maneuver sequence stored onboard the spacecraft executed nominally near periselene on 2011/178 from 14:04 to 16:31 UTC, slowing the spacecraft by 50.3 m/s and allowing gravity capture into an initial orbit with estimated periselene and aposelene radii of approximately 3,543 and 27,000 km, respectively.

This was a great team effort so far, and our special thanks go out to the JPL and GSFC navigation and flight dynamics teams, as well as to all who helped us with networks support, in particular the DSN team. We could not have accomplished this without you!

Manfred Bester
Mission Operations Manager
Space Sciences Laboratory, UC Berkeley

See NASA Press release here:

View from above the ARTEMIS P1 orbit as it transitions from the kidney-shaped Lissajous orbit to orbiting around the moon.
Credit: NASA/Goddard Space Flight Center.

August 25, 2010:

Artemis Spacecraft First to Enter New Type of Orbit:

Congrats to the ARTEMIS mission operations and mission design team for a successful capture of P1 into the Lunar Lagrange point L2! This is a technical milestone, as this orbit has never been entered into by other spacecraft, and paves the way for planning of future missions that can use the orbit as a staging ground for lunar insertions, or for continuous data relay from the far side. The L2 entry of P1 will be followed by an L1 entry of P2 in October 2010, commencing the beginning of ARTEMIS science operations with 2 spacecraft.

See NASA press release at:

Illustration of ARTEMIS-P1 librations orbits

February 26, 2010:

ARTEMIS P2 Completes Orbit Raise Maneuver Sequence:

As of February 26, 2010 the last orbit raise maneuver (ORM) of a long sequence was successfully executed on ARTEMIS P2 (THEMIS C), setting up this probe for a lunar flyby (on March 28), to initiate its trans-lunar trajectory (see image, left side). ARTEMIS P1 (THEMIS B) is already in its trans-lunar orbit, beyond 1,000,000 km from Earth (see image, upper right corner). At such large distances significant data recovery is impractical, so any data recovered on a best effort basis is primarily for the sake of checking health and status. This completes the period of ORMs successfully. Significant data recovery will commence again when the probes arrive at lunar distances starting in the fall, followed by capture into the Lissajous orbits. Hats off to the operations and mission design personnel for bringing the probes safely to this point!

ARTEMIS P2 completes orbit
raise maneuver sequence, shown
here en-route to trans-lunar

July 20, 2009:

A Small Step for Artemis, a Giant Leap for NASA Heliophysics:

40 years after Apollo 11's lunar landing, NASA's first dual identical-satellite mission to study the Moon and its environment commences operations. Artemis consists of the pair of outer THEMIS/MIDEX probes which will be repositioned starting today and over the course of the next year and a half and will utilize the lunar gravity to gradually purturb their orbits and provide a low-thrust lunar orbit capture. Artemis stands for "Acceleration Reconnection and Turbulence and Electrodynamics of the Moon's Interaction with the Sun." The mission was approved in May 2008 as part of the extended operations plan of THEMIS by NASA's 2008 Heliophysics Senior Review panel [see]. Artemis (which also denotes the goddess of the moon and hunting in ancient mythology) will utilize simultaneous measurements of particles and electric and magnetic fields from two locations to provide the first three-dimensional information on how energetic particle acceleration takes place near the moon's orbit, in the distant magnetosphere and in the solar wind. It will also perform unprecedented observations of the refilling of the space environment behind the dark side of the moon, the greatest known vacuum in the solar system, by the solar wind.
Pictorial representation of ARTEMIS probes around the moon, as they will orbit in early 2011. ARTEMIS P1 and P2 are the outermost two THEMIS probes, which commenced their low-thrust lunar orbit insertion maneuvers on July 20, 2009, slated to arrive at the moon in October 2010.

February 27, 2009:

Road Cleared for ARTEMIS Mission Implementation:

On Feb 24, 2009 ARTEMIS passed its mini-Confirmation review at GSFC. Therefore, the road has been cleared for the upcoming mission implementation. There will be a delta (pico) review in early May to ensure progress with contingency planning is adequate, but we don't anticipate any problems. Congratulations to the implementation teams at UCB, JPL and GSFC for their outstanding progress to-date!

The essence of the comments of the review board was that the ARTEMIS team has done an outstanding job, especially considering the little (8 months) time that has passed since the Senior Review go-ahead. Of course, it was recognized that there is still a lot of work ahead, but the team yesterday presented a reasonable, viable plan, which conveys confidence they can deliver. Even though this is a challenging project, given the resources and time available, this condition was deemed acceptable considering that the THEMIS probes are already operating well and this is an extended-phase mission. The reviewers have come up with less than a handful of requests for action, which I am certain will strengthen the project, as it moves towards the Orbit Raise Maneuvers in the upcoming summer. Tentatively the ORMs start July 9th.

THEMIS P1 (TH-B) in red and P2 (TH-C) orbit between this summer's orbit raise maneuvers and October 2010 when they will capture the Lagrange points between Earth and Moon. After six months in those orbits, P1 and P2 will be inserted into Lunar orbits where they will make measurements of the Lunar warke, the magnetotail, and the solar wind through September 2012. View larger figure.

May, 2008:

ARTEMIS Mission Approved by NASA:

NASA has extended the THEMIS mission to the year 2012. In addition, ARTEMIS, a new mission that will take the two outer THEMIS probes into lunar orbits and perform solar wind, magnetotail, and lunar science, has been provisionally approved by NASA, pending a technical review before February 2009. Excerpt from the senior review report: "The senior review panel congratulates the THEMIS science team on their innovative plan to drastically reposition the five THEMIS probes at the conclusion of the prime THEMIS mission. The extended mission, which will consist of THEMIS-Low and the lunar-orbitting ARTEMIS, is highly compelling, both for the individual scientific goals and what will undoubtedly be their excellent contributions to the Helio-Physics Great Observatory." ARTEMIS will perform measurements in the lunar environment from October 2010 until September 2012.

Please find the extended THEMIS proposal here.
Please find the Senior Review report here.