Science Atmospheric Science


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Apr 5, 2015
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Exploding stars help to understand thunderclouds on Earth

22-Apr-2015 University of Groningen


This shows a particle shower initiated by a cosmic ray reaches LOFAR through a thundercloud.

How is lightning initiated in thunderclouds? This is difficult to answer - how do you measure electric fields inside large, dangerously charged clouds? It was discovered, more or less by coincidence, that cosmic rays provide suitable probes to measure electric fields within thunderclouds. This surprising finding is published in Physical Review Letters on April 24th. The measurements were performed with the LOFAR radio telescope located in the Netherlands.

'We used to throw away LOFAR measurements taken during thunderstorms. They were too messy.' says astronomer Pim Schellart. 'Well, we didn't actually throw them away of course, we just didn't analyze them.' Schellart, who completed his PhD in March this year at Radboud University in Nijmegen and is supervised by Prof. Heino Falcke, is interested in cosmic rays. These high-energy particles, originating from exploding stars and other astrophysical sources, continuously bombard Earth from space.

High in the atmosphere these particles strike atmospheric molecules and create 'showers' of elementary particles. These showers can also be measured from the radio emission that is generated when their constituent particles are deflected by the magnetic field of the Earth. The radio emission also gives information about the original particles. These measurements are routinely conducted with LOFAR at ASTRON in Dwingeloo, but not during thunderstorms.


That changed when the data were examined in a collaborative effort with astrophysicist Gia Trinh, Prof. Olaf Scholten from the University of Groningen and lightning expert Ute Ebert from the Centrum Wiskunde & Informatica in Amsterdam.

'We modeled how the electric field in thunderstorms can explain the different measurements. This worked very well. How the radio emission changes gives us a lot of information about the electric fields in thunderstorms. We could even determine the strength of the electric field at a certain height in the cloud.' says Schellart.

This field can be as strong as 50 kV/m. This translates into a voltage of hundreds of millions of volts over a distance of multiple kilometers: a thundercloud contains enormous amounts of energy.

Dangerous charge

Lightning is a highly unpredictable natural phenomenon that inflicts damage to infrastructure and claims victims around the world. This new method to measure electric fields in thunderclouds will contribute to a better understanding and ultimately better predictions of lightning activity. Current measurement methods from planes, balloons or little rockets are dangerous and too localized. Most importantly the presence of the measurement equipment influences the measurements. Cosmic rays probe the thunderclouds from top to bottom. Moving at almost the speed of light they provide a near instantaneous 'picture' of the electric fields in the cloud. Moreover, they are created by nature and are freely available.

'This research is an exemplary form of interdisciplinary collaboration between astronomers, particle physicists and geophysicists', says Heino Falcke. 'We hope to develop the model further to ultimately answer the question: how is lightning initiated within thunderclouds?'

UNH Physicist Finds Mysterious Anti-electron Clouds Inside Thunderstorm

May 12, 2015

DURHAM, N.H. – A terrifying few moments flying into the top of an active thunderstorm in a research aircraft has led to an unexpected discovery that could help explain the longstanding mystery of how lightning gets initiated inside a thunderstorm.

University of New Hampshire physicist Joseph Dwyer and lightning science colleagues from the University of California at Santa Cruz and Florida Tech describe the turbulent encounter and discovery in a paper to be published in the Journal of Plasma Physics.

In August 2009, Dwyer and colleagues were aboard a National Center for Atmospheric Research Gulfstream V when it inadvertently flew into the extremely violent thunderstorm—and, it turned out, through a large cloud of positrons, the antimatter opposite of electrons, that should not have been there.

To encounter a cloud of positrons without other associated physical phenomena such as energetic gamma-ray emissions was completely unexpected, thoroughly perplexing and contrary to currently understood physics.

“The fact that, apparently out of nowhere, the number of positrons around us suddenly increased by more than a factor of 10 and formed a cloud around the aircraft is very hard to understand. We really have no good explanation for it,” says Dwyer, a lightning expert and the UNH Peter T. Paul Chair in Space Sciences at the Institute for the Study of Earth, Oceans, and Space.

It is known that thunderstorms can sometimes make flashes of energetic gamma rays, which may produce pairs of electrons and positrons when they interact with air. But the appearance of positrons should then coincide with a large increase in the number of gamma rays.

“We should have seen bright gamma-ray emissions along with the positrons,” Dwyer says. “But in our observations, we first saw a positron cloud, then another positron cloud about seven kilometers away and then we saw a bright gamma-ray glow afterwards. So it’s all not making a whole lot of sense.”

Adds coauthor David Smith of the UC Santa Cruz, "We expected the thunderstorm to make some forms of radiation but not this. We don't even know whether it’s something nature can do on its own or only happens when you toss an airplane into the mix."
The physical world is filled with normal matter and antimatter. For every normal particle there’s an antiparticle, such as an electron and its associated anti-particle, called the positron, which, when brought together, annihilate each other in a flash of gamma rays. It is, Dwyer points out, the very same process that is supposed to power Star Trek’s Starship Enterprise.

Having boldly gone where few people should, Dwyer says the experience inside the belly of the beast provides further insight into the bizarre and largely unknown world of thunderstorms—an alien world of gamma rays, high-energy particles accelerated to nearly the speed of light and strange clouds of antimatter positrons.

One possible explanation for the sudden appearance of positrons is that the aircraft itself dramatically influenced the electrical environment of the thunderstorm but that, Dwyer says, would be very surprising. It’s also possible the researchers were detecting a kind of exotic electrical discharge inside the thunderstorm that involves positrons.

“This is the idea of ‘dark lightning,’ which makes a lot of positrons,” says Dwyer. “In detecting the positrons, it’s possible we were seeing sort of the fingerprint of dark lightning. It’s possible, but none of the explanations are totally satisfying.”

Dark lightning is an exotic type of electrical discharge within thunderstorms and is an alternative to normal lightning. In dark lightning, high-energy particles are accelerated and produce positrons, which help discharge the electric field.

Says Dwyer, “We really don’t understand how lightning gets started very well because we don’t understand the electrical environment of thunderstorms. This positron phenomenon could be telling us something new about how thunderstorms charge up and make lightning, but our finding definitely complicates things because it doesn’t fit into the picture that was developing.”

The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling 13,000 undergraduate and 2,500 graduate students.
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Caption: Lightning and severe weather are two of the most visible products of thunderstorms. However, scientists are discovering that the storms also contain a fascinating variety of strange phenomena, including powerful gamma-ray flashes and puzzling clouds of positrons—the anti-matter version of the electron.
UNH Scientists Show -Breaking Waves - Perturb Earth's Magnetic Field

May 11, 2015

DURHAM, N.H. -- The underlying physical process that creates striking “breaking wave” cloud patterns in our atmosphere also frequently opens the gates to high-energy solar wind plasma that perturbs Earth’s magnetic field, or magnetosphere, which protects us from cosmic radiation. The discovery was made by two University of New Hampshire space physicists, who published their findings in the online journal Nature Communications Monday, May 11, 2015.

The phenomenon involves ultra low-frequency Kelvin-Helmholtz waves, which are ubiquitous throughout the universe and create the distinctive patterns—from Earth’s clouds and ocean surfaces to the atmosphere of Jupiter—but were not thought to be a common mechanism for changing the dynamics of the magnetosphere.

“Our paper shows that the waves, which are created by what’s known as the Kelvin-Helmholtz instability, happens much more frequently than previously thought,” says coauthor Joachim “Jimmy” Raeder of the UNH Space Science Center within the Institute for the Study of Earth, Oceans, and Space. “And this is significant because whenever the edge of Earth’s magnetosphere, the magnetopause, gets rattled it will create waves that propagate everywhere in the magnetosphere, which in turn can energize or de-energize the particles in the radiation belts.”

Using data from NASA’s Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, Raeder and his Ph.D. student Shiva Kavosi (lead author) found that Kelvin-Helmholtz waves actually occur 20 percent of the time at the magnetopause and can change the energy levels of our planet’s radiation belts.

These changing energy levels can have impacts on how the radiation belts either protect or threaten spacecraft and Earth-based technologies. But Raeder notes the finding is less about the affects of so-called “space weather” on space- and Earth-based communications and more about a better understanding of the basic physics of how the magnetosphere works.

“It’s another piece of the puzzle,” Raeder says. “Previously, people thought Kelvin-Helmholtz waves at the magnetopause would be rare, but we found it happens all the time.”

The effect of Kelvin-Helmholtz instability waves (named for 19th century scientists Lord William Thomson Kelvin and Hermann von Helmholtz) can commonly be seen in cloud patterns, on the surface of oceans or lakes, or even a backyard pool. The distinctive waves with capped tops and cloudless troughs are created by what’s known as velocity shear, which occurs when a fluid or two different fluids—wind and water, for example—interact at different speeds to create differing pressures at the back and front ends of the wave.

Notes Kavosi, “In clouds, you see it because the lower atmosphere is more stagnant and you have a higher speed wind going over it, which creates that distinctive swirl pattern. The phenomenon is really ubiquitous in nature. Often, the waves are present in the atmosphere but not visible if there are no clouds. In that case, pilots cannot see them and aircraft may experience severe and unexpected turbulence.”

The five-satellite THEMIS mission launched in 2007 and has provided a unique, long-term dataset that allowed Kavosi and Raeder to do robust statistical analysis of the occurrence of Kelvin-Helmholtz waves. Raeder has been a co-investigator on the THEMIS mission since its conception more than 15 years ago and continues to analyze the data in collaboration with his graduate students.

“Previous missions were either too short or the observations didn’t occur in the right place,” Raeder says. “THEMIS’s elliptical orbits achieved over one thousand magnetopause crossings and provided unprecedented observations. We didn’t have a database like this before and therefore couldn’t do the analysis.”

The Nature Communications paper, "Ubiquity of Kelvin-Helmholtz waves at Earth's magnetopause,” can be viewed at
The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling 13,000 undergraduate and 2,500 graduate students.

Image to download:

Caption: Kelvin-Helmholtz waves in the atmosphere form when high-speed wind blows over more stagnant air masses. The waves create turbulence and mix the air masses. New research has shown that similar Kelvin-Helmholtz waves also frequently occur in Earth’s magnetosphere and allow particles from the solar wind to enter the magnetosphere to produce oscillations that affect Earth’s protective radiation belts. Credit: Copyright University Corporation for Atmospheric Research, photo by Benjamin Foster.
Volcanic Lightning: How does it work?

Mar 29, 2013


Volcanic lightning strikes during an eruption of Japan's Sakurajima volcano in February 2013.

The fusion of flash with ash! Say the words aloud, together, and it sounds impossible – the kind of thing a six-year-old might think up. And yet, volcanic lightning is very real. But how does it happen?

Few phenomena can compete with the raw beauty and devastating power of a raging thunderstorm, save for a particularly violent volcanic eruption. But when these two forces of nature collide, the resulting spectacle can be so sublime as to defy reason.

The photograph above offers some important insights into the formation and study of volcanic lightning. It was taken late last month by German photographer Martin Rietze, on a visit to Japan's Sakurajima volcano. Only very big eruptions, he tells us via email, can generate major thunderbolts like the ones seen above.

Smaller eruptions tend to be accompanied by more diminutive storms, which can be difficult to spot through thick clouds of ash. What's more, lightning activity is highest during the beginning stages of an eruption, making it all the more challenging to capture on film. Photographing a big volcanic event at any stage is hard enough as it is; if you're not nearby when it happens, says Rietze, "you will always arrive too late."

It turns out the same things that make volcanic lightning hard to photograph also make it difficult to study. The first organized attempt at scientific observation was made during Iceland's Surtsey eruption in 1963 (pictured here). The investigation was later recounted in a May 1965 issue of Science:

"Measurements of atmospheric electricity and visual and photographic observations lead us to believe that the electrical activity is caused by the ejection from the volcano into the atmosphere of material carrying a large positive charge."

Translation? Volcanic lightning, the researchers hypothesize, is the result of charge-separation. As positively charged ejecta makes its way skyward, regions of opposite but separated electrical charges take shape. A lightning bolt is nature's way of balancing the charge distribution. The same thing is thought to happen in regular-old thunderstorms. But this much is obvious, right? So what makes volcanic lightning different?

Close to 50 years have transpired since Surtsey exploded in November 1963. Since then, only a few studies have managed to make meaningful observations of volcanic eruptions. One of the most significant was published in 2007, after researchers used radio waves to detect a previously unknown type of lightning zapping from the crater of Alaska's Mount Augustine volcano in 2006.

"During the eruption, there were lots of small lightning (bolts) or big sparks that probably came from the mouth of the crater and entered the (ash) column coming out of the volcano," said study co-author Ronald J. Thomas in a 2007 interview with National Geographic. "We saw a lot of electrical activity during the eruption and even some small flashes going from the top of the volcano up into the cloud. That hasn't been noticed before."

The observations suggest that the eruption produced a large amount of electric charge, corroborating the 1963 hypothesis – but the newly identified lightning posed an interesting puzzle: where, exactly, do these charges come from? "We're not sure if it comes out of the volcano or if it is created just afterwards," Thomas explains. "One of the things we have to find out is what's generating this charge."

Since 2007, a small handful of studies have led to the conclusion that there exist at least two types of volcanic lightning – one that occurs at the mouth of an erupting volcano, and a second that dances around in the heights of a towering plume (an example of the latter occurred in 2011 above Chile's Puyehue-Cordón Caulle volcanic complex, as pictured here. (Photograph by Carlos Gutierrez/Reuters.) Findings published in a 2012 article in the geophysics journal Eos reveal that the largest volcanic storms can rival the intensity of massive supercell thunderstorms common to the American midwest. Still, the source of the charge responsible for this humbling phenomenon remains hotly debated.

One hypothesis, floated by Thomas' team in 2007, suggests that magma, rock and volcanic ash, jettisoned during an eruption, are themselves electrically charged by some previous, unknown process, generating flashes of electricity near the volcano's opening. Another holds that highly energized air and gas, upon colliding with cooler particles in the atmosphere, generate branched lightning high above the volcano's peak. Other hypotheses, still, implicate rising water and ice-coated ash particles.

"What is mostly agreed upon," writes geologist Brentwood Higman at, "is that the process starts when particles separate, either after a collision or when a larger particle breaks in two. Then some difference in the aerodynamics of these particles causes the positively charged particles to be systematically separated from the negatively charged particles." You can see the diagram here.

The exciting thing about this process is that these differences in aerodynamics, combined with various potential sources of charge (magma, volcanic ash, etc) suggest that there may actually be types of volcanic lightning we've yet to observe. As Martin Uman, co-director of the University of Florida Lightning Research program, told NatGeo back in 2007: "every volcano might not be the same."
Calbuco volcanic lightnings

Apr 24, 2015

For the first time in more than 42 years, the Calbuco volcano in southern Chile has erupted. Two blasts in 24 hours on April 22nd sent plumes of ash and volcanic gases shooting at least 50,000 feet high, well into the altitudes where planes fly. One of the eruptions occured at night and put on a spectacular display of volcanic lightning:





Spectacular images of the subplinian eruption column and plume at day and night, including volcanic lightning, are emerging everywhere on the net.

VAAC Buenos Aires reports ash to 40,000 ft (12 km) altitude while other sources speak of heights up to 15-20 km.

Night video
A spectacular video shows the lower part of the erupting jet of incandescent tephra (ash and bombs) during the eruption as well as lightnings
Red sprites, blue jets and elves


Tornado chasing, quite the vogue these days, wears out one's car, burns up gasoline, and taxes the nerves of even the hardiest of twister trackers. But there are other mysterious, thunderstorm-related phenomena that can be viewed above distant thunderheads in the peace and tranquillity of a summer night while sitting in a rocking chair on your back porch. Less than ten years ago, nobody had heard of sprites, blue jets and elves, in fact, the terms hadn't even entered the meteorological vocabulary. Recent research, however, has confirmed over a century of frequent but generally ignored observations of an entire menagerie of strange, luminous, lightning-related flashes dancing high above thunderstorm tops. And you can, if you know how, observe some of these with the naked eye. Here's the story of how sprites were discovered and how you might be able to spot some on your own.

In past decades, the textbooks said weather stopped at the tropopause, the layer separating the turbulent troposphere from the quiescent stratosphere above. Not so. As long ago as 1886, people were publishing reports in which they struggled to describe momentary discharges of "lightning," for lack of a better term, that they had observed high above storm clouds.

A 1903 paper discussed "rocket lightning ... a luminous tail ... shooting straight up ... rather faster than a rocket..."

From Africa in 1937 came reports of "long and weak streamers of reddish hue...some 50 kilometers high..."

English scientific papers from the 1950s detailed what seemed to be flames appearing to shoot above thunderstorms near the horizon. Recently Earle Williams of the Massachusetts Institute of Technology took a closer look at a nighttime photograph of an Australian thunderstorm in his possession since the late-1980s. A lightning channel extending into the clear air above the storm top in turn appears to have "blue flame" fanning upward, perhaps even into the stratosphere. An airline passenger over Texas reported he saw over twenty faint plumes of light "extending from the top of the thunderhead above the pool of light from the lightning discharge..." Many of these observations were collected in books of meteorological esoterica alongside reports of turtles encased in hailstones, half meter wide snow flakes and showers of toads, fish, seeds and whatnot. Interesting, but what could be the relevance of such events variously termed "cloud-to-stratosphere lightning", "upward lightning" or "cloud-to-space" lightning?

One clue was offered in 1956 by Nobel Prize winning physicist C.T.R. Wilson who himself once saw "diffuse fan-shaped flashes of greenish color extending upward into the clear sky...". He speculated than such discharges between cloud tops and the ionosphere might be a normal accompaniment of lightning discharges to earth, but ones which are visible only under very special conditions. These might represent a heretofore unknown component of the global electrical circuit. Then, in 1989, by pure chance, University of Minnesota scientists John Winckler, Robert Franz and Robert Nemzek, while testing a low-light video camera for a high altitude scientific rocket shot, captured two fields of video showing giant twin pillars of light extending upward more than 30 kilometers above a distant thunderstorm. With the hard evidence now in hand, the race was on in mainstream scientific circles to find out what was going on way up there.

NASA scientists from the Marshall Space Flight Center soon found over a dozen examples of strange 'upward lightning' bolts in the routine video recordings of the horizon taken by the Space Shuttle's low-light payload bay camera. After reviewing the many dozens of anecdotal reports of these events, the author played a hunch as to how to "capture" these creatures on tape. The evidence suggested that these flashes occurred above the anvils of exceptionally large thunderstorm systems. At our rural laboratory, the Yucca Ridge Field Station, situated near Fort Collins on the High Plains east of the Colorado Front Range, we waited for the right conditions, big thunderstorm clusters that were far enough away so we could easily view the stratosphere and mesosphere region above their anvil canopies.

On the night of 7 July 1993, giant thunderstorms were boiling over Kansas and Nebraska, one of the series of mesoscale convective complexes that drowned the midwest in record setting flooding rains far to the east. We aimed a low-light video camera, cousin to the night scopes used by the military, to the east and began taping. For the first two hours, not much happened, except for the almost continuous flashing of lightning within the distant clouds. Then, suddenly, a bright flash occurred high above the storm tops (appearing white on the monochrome television system screen). Over the next several hours, over 240 high altitude flashes were captured. The very next night, University of Alaska scientists obtained similar images from a high-flying NASA aircraft over Iowa. Since then, thousands of flashes have been recorded on low-light video from the ground and from air. While easily visible on the television monitor on that very first night, I was unable to see anything with the naked eye while staring above the distant clouds. But several nights later, when the show started again, with some patience, and dark adapted eyes, there they were, bright reddish curtains dancing a gossamer ballet high above the storm clouds.

In 1994, while flying an extremely sensitive color camera normally used for auroral photography, University of Alaska scientists confirmed that the flashes indeed have a generally reddish color, but which often fades to purple or blue in the downward extending tendrils.

The flashes were named sprites after the creatures in Shakespeare's "The Tempest," in part because of their transient, ephemeral nature. But unlike the bard's characters, these sprites are very real indeed.

And the sprites were soon found to have company. At least two other distinct phenomena have been discovered to date. While flying near an especially active hailstorm in Arkansas, the University of Alaska team were startled to see blue beams of light shooting upward directly out of cloud tops at speeds over 100 kilometers a second. They reached heights of 40 or 50 kilometers (two or three times the cloud heights) before fading away. Around 50 of these "blue jets" were seen that night. But the blue jet seems to be very rare. In four years of ground monitoring, only one blue jet has been captured on tape. The discovery of the blue jet does explain many of the strange reports over the last century that did not seem to jibe with the characteristics of red sprites. It appears that the blue jet can be seen with the naked eye, if you are lucky enough to be around on a dark night when that rare storm produces them. Based only on a few sparse reports, intense hailstorms may be the best candidates for uncorking blue jets.

After the red sprites and blue jets came the elves. In 1995, scientists from the University of Tohoku (Japan) and Stanford University, working with other science teams at the Yucca Ridge Field Station, confirmed the presence of elves (emissions of light and VLF perturbations from EMP sources). These were actually predicted by theorists before they were ever caught on tape. The elves appear as giant expanding disks of light between 70 and 100 kilometers altitude. They are caused by the passage through the ionosphere of the electromagnetic pulse (EMP), the intense radio waves emitted from powerful lightning flashes. Though huge, sometimes expanding to more than 400 kilometers in diameter, the elves are so transient (less than one-thousandth of a second), it is unlikely the human eye could detect them.

But the red sprites can be seen by the naked eye. They are by far the most common of these mesospheric creatures, and we know where they "live". So a plan for some serious "sprite hunting" is relatively easy to develop.

Sprites come in a bewildering variety of sizes and shapes. They can look like giant red blobs, picket fences, upward branching carrots, or tentacled octopi. The sprite luminosity can extend upward as high as 95 km, with the brightest part usually located between 50 and 75 km altitude. The often bluish tendrils can sometimes extend downward below 30 km, close to, but probably not touching, the cloud tops. Sprites can occur singly or in clusters which sometimes fan out for over 150 kilometers. Sprites appear to be uniquely associated with cloud-to-ground (CG) flashes of positive polarity, usually those having peak currents larger than most of the other positive CG events in the storm. By comparison to the pencil-thin channel of their parent positive CG flash, the volume illuminated by a large sprite can reach hundreds or even thousands of cubic kilometers.

So now that we know about all the 'electrical action' above the clouds, a natural question is - can we see and photograph them? The answer is yes... and no. Taking standard photographs will not work unless you have a film with an ISO of 2 million (don't bother to ask for it in the photo store). To take images, you need a low-light video system. This is well within the reach of well-funded scientific investigators, but not your average storm watcher. Yet under ideal viewing conditions you can indeed see sprites with the naked eye. Here's how.

Sprites occur high above very large thunderstorm systems. Since they are so high up, it is much easier to see them if they are at least 50 to 100 kilometers away. Sprites have been visually detected as far as 400 km out, but those occurrences are rare. Not every thunderstorm produces sprites, even if it has vigorous lightning. To improve your chances, check out the radar echoes on your local TV or the Weather Channel. Look for thunderstorm clusters that combined are at least 150 kilometers on a side. If you have access to data from the National Lighting Detection Network, look above the part of big storms where the positive CGs are occurring. This is most often in the large stratiform or anvil region of storm systems.

To actually view the sprites, find a location with a good view of the horizon. The further away from the city lights, the better. It is best to choose a dark night with no moonlight. In the eastern and southern United States, unfortunately, haze and air pollution can sometimes blot out the sprites. Let your eyes adapt to the dark for at least ten minutes. Look in the direction of the big storms. If you can see the illuminated tops of the distant storms, shield your eyes (a piece of cardboard can help) from the lightning flashing within the clouds. Concentrate your gaze at an altitude about four to five times the height of the cloud top, not the storm itself. Then be patient. In the more active storms, sprites can occur every one or two minutes, but every five to ten minutes is more common. They only last from one one-hundredth to one-tenth of a second. Blink and you can miss one. Due to a quirk in human night vision, you are often more likely to perceive them out of the corner of your eye. What will you see? To many it looks like the aurora borealis turning on and off in an instant. The true sprite color is salmon red, but at such low light levels the eye can play tricks on you and you might perceive them as green, orange or white. If you are looking in the right place and think you saw something, you probably did.

The best places in North America for sprite watching? Probably above the northern High Plains and upper midwest in a broad belt from Colorado to North Dakotas over to Minnesota and down into Texas. But they do occur above big storms worldwide, and have been spotted from aircraft and the Space Shuttle above Panama, Peru, Africa, Australia and Indonesia, to name a few places.

The more scientists look above thunderstorms, the more they find. Researchers have been making measurements with satellites, spectrometers, and photometers, and probing with radars and radio waves. It is clear that these progeny of thunderstorm lightning flashes can influence upper atmospheric electrical structure, radio transmissions, and perhaps the chemistry of the stratosphere and mesosphere. The mystery is just beginning to be unraveled. Theoreticians are furiously proposing and testing many mathematical models for sprites, jets and elves. Learned discussions abound in technical journals about electromagnetic pulses, breakdown from quasi-electrostatic fields generated by massive shifts of hundreds of coulombs of charge within giant storm clouds, and runaway electrons accelerating to energies above a million electron volts in the intense electric fields above the storms. But for most of us, the sprite is a chance to spend a calm evening on the porch, or perhaps on the tailgate of a chase vehicle that never did quite catch the tornado, and just contemplate what's up there. And to wonder. What else might nature be willing to tell us if we keep looking very carefully, and we don't blink.


Phenomena occurring in Earth’s upper atmosphere. Credits: CNES.
Giant Red Sprite Seen From Space Station

The crimson electrical outburst (center right) is estimated at 30 miles tall.

Sprites form at plasma irregularities in the lower ionosphere

May 7, 2014

Atmospheric sprites have been known for nearly a century, but their origins were a mystery. Now, a team of researchers has evidence that sprites form at plasma irregularities and may be useful in remote sensing of the lower ionosphere.

"We are trying to understand the origins of this phenomenon," said Victor Pasko, professor of electrical engineering, Penn State. "We would like to know how sprites are initiated and how they develop."

Sprites are an optical phenomenon that occur above thunderstorms in the D region of the ionosphere, the area of the atmosphere just above the dense lower atmosphere, about 37 to 56 miles above the Earth. The ionosphere is important because it facilitates the long distance radio communication and any disturbances in the ionosphere can affect radio transmission.

"In high-speed videos we can see the dynamics of sprite formation and then use that information to model and to reproduce the dynamics," said Jianqi Qin, postdoctoral fellow in electrical engineering, Penn State, who developed a model to study sprites.

Sprites occur above thunderstorms, but thunderstorms, while necessary for the appearance of a sprite, are not sufficient to initiate sprites. All thunderstorms and lightning strikes do not produce sprites. Recent modeling studies show that plasma irregularities in the ionosphere are a necessary condition for the initiation of sprite streamers, but no solid proof of those irregularities existed.

The researchers studied video observations of sprites, developed a model of how sprites evolve and disappear, and tested the model to see if they could recreate sprite-forming conditions. They report their results today (May 7) in Nature Communications.

Sprites resemble reddish orange jellyfish with bluish filamentary tendrils hanging down below.

Careful examination of videos of sprites forming showed that their downward hanging filaments form much more rapidly than in the horizontal spread, leading the researchers to suggest that localized plasma irregularities cause the streamers to propagate.

The researchers used a two-dimensional cylindrical symmetric plasma fluid model, a mathematical model of the ionization movements in the sprite, to study sprite dynamics. They then used the model to recreate optical sprite creation. From this recreation, the researchers determined where the sprite streamers originated, and they could estimate the size of the plasma irregularity.

Further analysis suggested some potential causes of these plasma irregularities. The most obvious seems to be the existence in that area of a previous sprite. For the sprites examined, there were no previous sprites in that area that occurred close enough in time, unless there were long-lasting irregularities. However, the researchers are unsure how such long-lasting events could occur.

Another possible source for the irregularities is meteor events. The D region of the ionosphere is in the upper part of the atmosphere where most meteors can exist, because once they enter the denser, lower atmosphere, they burn up due to atmospheric friction.

"This technique can be used for remote sensing in the ionosphere as well," said Pasko. "Using high speed videos and fluid models we may be able to see other things that go on in the ionosphere and better understand the effects of various natural phenomena on very low frequency radio communications."

Also working on this project were Matthew G. McHarg, professor of physics and director, United States Air Force Academy Space Physics and Atmospheric Research Center, and Hans C. Stenbaek-Nielsen, professor of geophysics emeritus, University of Alaska, Fairbanks.

The National Science Foundation and the Defense Advanced Research Projects Agency supported this work.

The Everlasting Lightning Storm of Venezuela

October 13, 2014

There is a place in Venezuela that is home to a bizarre, raging storm that almost never ceases. It is a vast, throbbing beast of a storm that thrums with continual lightning and bellows forth with thunder; an object of singular, electrifying intensity that seems more like an angry living thing than a mere weather phenomenon. In this place, for sometimes up to nearly 300 days a year, the lightning sizzles across the sky and licks at the earth below in a dazzling display of nature at its rawest and most furious. Here, in one, tiny, swampy corner of Venezuela the storm beast makes its lair, and produces the most breathtaking spectacle of a natural light show on earth.

This mesmerizing atmospheric phenomenon is known as Relámpago del Catatumbo, or Catatumbo lightning, and it only occurs in one very defined area of Venezuela, at the mouth of the Catatumbo River where it empties into Lake Maracaibo, in the state of Zulia. Here, the lightning almost never stops and it is startling in its intensity. For between 200 and 300 days a year, the storm produces an average of 28 strikes of lightning per minute for up to 10 hours at a time, sometimes unleashing up to 3,600 bolts of lightning per hour, or roughly one per second during particularly explosive displays, culminating in upwards of 40,000 lightning strikes a night. The National Weather Service calls 12 strikes per hour “excessive,” so yeah, it’s a lot of lightning. This immense amount of lightning is the single largest natural source of ozone in the world and is unique on this planet.

This lightning is not only produced in excessively large amounts, but is also remarkably powerful, with each bolt ranging from between 100,000 to 400,000 amps, far beyond the norm. This frighteningly potent lightning is so incredibly bright and constant that it is visible from up to 250 miles away, as a haunting, angry, flickering glow upon the horizon. This long distance visibility has led to the commonly held myth that the Catatumbo lightning is silent, since it can be seen from much farther away than its thunder can be heard. However, it does produce thunder, as all lightning does, in a a cacophony of unfettered, undiluted, raw noise. Nowhere else on Earth does lightning strike in such concentrations and with such relentless ferocity. The storm is also remarkably predictable, occurring in the exact same place every time, and starting practically on cue at around the same time, every time, just about an hour after dusk.

The Catatumbo lightning phenomenon has been well known for centuries. Natives of the region once referred to it as rib a-ba, or the “river of fire,” and revered it as a sign from the gods. Later, during the colonial period of the Caribbean, the highly visible light show was used as a means of navigation by sailors, who called it the “Lighthouse of Catatumbo” and the “Maracaibo Beacon.” The perpetual lightning storm also had a hand in changing history itself, as it was instrumental in the failure of at least two attempted surprise nighttime invasions of Venezuela. The lightning first betrayed the English Sir Francis Drake in 1595, lighting up the nocturnal invasion fleet and alerting nearby Spanish forces. In 1823, the Catatumbo lightning once again worked to thwart an invasion when it illuminated a Spanish fleet trying to sneak ashore under the cover of darkness during the Venezuelan War of Independence.

In addition to the sheer, staggering intensity of the storm is its continually shifting appearance. Depending on the level of humidity in the air on a particular night, the lightning bolts appear as different colors, and can even phase from one color to another in a single night. When air moisture is high, the minuscule airborne droplets of water act as a prism to scatter light and cause the lightning to become stunning explosions of brilliant red, pink, orange, and purple. When the air is dry, the lightning becomes crackling shocks of stark white in the absence of the prism effect.

This natural display of spectral beauty has its share of mysteries. For all of its majestic beauty and terrifying power, it has long been unclear as to what actually causes this ongoing storm to become so amped up and only in one small, well defined area. The most common explanation is that a combination of the unique topography and atmospheric conditions of the area, such as wind and heat, cause and feed the terrifying storm. The Lake Maracaibo Basin is surrounded on three sides by the Andes mountains, which form a sort of V that traps warm trade winds from the Caribbean. This hot air meets the cooler air descending from the mountains and the clash causes condensation. This condensation, plus the updrafts created by the additional moisture evaporating from the lake itself, creates the perfect recipe for the formation of thunderstorms.

It is also believed that the unique concentration and intensity of the lightning here can be attributed to the large reserves of methane that lie in the ground beneath the area. The Maracaibo basin sits atop one of the largest oil fields in the world, which produces vast quantities of methane gas. The theory is that this methane may seep into the atmosphere and increase conductivity, giving the thunderstorms and lightning an extra boost. Methane has sometimes been attributed to the myriad colors the lightning takes on as well. While undoubtedly there is a lot of methane to be found here, and it is now understood in particular concentrations under the epicenter of the storm activity, it is unclear how much of an influence, if any, it exerts on the storm. One popular theory in the 1960s was that uranium embedded in the bedrock of the basin might have some effect on the storm. Yet for all of the ideas put forth, at this point, it is not totally understood what causes the storm to rage so consistently and violently.

Another mystery to be found in the storm of Catatumdo is its tendency to suddenly stop for long periods. Although the lightning occasionally abates for short times, in 2010, after over a century of consistent, almost daily barrages of lightning, the Catatumbo storm suddenly and inexplicably ceased for over 6 weeks. With completely dark skies lasting from the end of January to the beginning of March, 2010, it was the longest calm in 104 years, so long in fact that scientists and people of the region feared that the rage of the storm had finally been spent. It was speculated that climate change and a drought caused by 2009’s powerful El Niño had conspired to snuff the lightning out forever. Then, as suddenly as it had gone quite, the storm once again roared to life to scorch the skies with its crackling lightning. No one is quite sure why the storm suddenly goes through quiet periods such as this, but they occur from time to time without warning. It is feared that ever increasing climate change could one day put an end to this unique and miraculous natural wonder forever.

For now, the Catatumbo lightning storm continues to light up the sky as it always has. It has become such a valued part of the country that Venezuela considers it a gift and a national treasure. The state where the storm occurs, Zulia, even features the lightning on its flag. The country is so proud of its never ending storm that it is actually pursuing plans to register the storm and its area as a UNESCO World Heritage Site, a classification that would be completely new for the organization as it typically only recognizes actual physical places. So far, these plans have not gone through, but the area does have the distinction of holding the Guinness World Record for most lightning strikes per square kilometer per year.

The Maracaibo Lake region and its Catatumbo lightning have become a big draw for tourists and scientists from all over the world, who come to study and experience the awe of this unrivaled natural spectacle. The country has made efforts to develop the area and turn the region into an eco-tourism zone to capitalize on the interest the storm has generated. This has proven to be difficult, as the region is infamous for harboring a myriad of drug dealers and armed guerilla groups, to the extent that the U.S. State Department advises against travel into the area. Nevertheless, looking at the raw power and beauty of this incredible natural phenomenon, one wonders if it may actually be worth it to make the journey.

This place is truly a unique, beautiful, and sometimes terrifying example of nature at its most furious. One can only hope that the continual transformation of our climate by humankind does not one day extinguish this unparalleled natural wonder forever.






Radiation belts in the region of the South-Atlantic magnetic anomaly

25 August, 1967

A number of spaceship-satellites flying around the earth at altitudes of 200-300 km was launched from the U.S.S.R. in 1960.

It appeared that during flights over some regions of the globe, the counters detected a considerably higher radiation level as compared with other regions. Considerable increase in the radiation intensity was observed in the South Atlantic especially.

South Atlantic Magnetic Anomaly

The Earth is surrounded by a pair of concentric donut-shaped clouds called the Van Allen radiation belts which, like magnetic bottle, store and trap charged particles from the solar wind. They are aligned with the magnetic axis of the Earth, which is tilted by 11 degrees from the rotation axis of the Earth, and are not symmetrically placed with respect to the Earth's surface. Although the inner surface is 1200 - 1300 kilometers from the Earth's surface on one side of the Earth, on the other they dip down to 200 - 800 kilometers. Above South America, about 200 - 300 kilometers off the coast of Brazil, and extending over much of South America, the nearby portion of the Van Allen Belt forms what is called the South Atlantic Anomaly. Satellites and other spacecraft passing through this region of space actually enter the Van Allen radiation belt and are bombarded by protons exceeding energies of 10 million electron volts at a rate of 3000 'hits' per square centimeter per second. This can produce 'glitches' in astronomical data, problems with the operation of on-board electronic systems, and premature aging of computer, detector and other spacecraft components.

The Hubble Space Telescope passes through the 'SAA' for 10 successive orbits each day, and spends nearly 15 percent of its time in this hostile region. Astronauts are also affected by this region which is said to be the cause of peculiar 'shooting stars' seen in the visual field of astronauts.


Earth's magnetic field in June 2014 as observed by the Swarm constellation, released on June 19, 2014 (Image credit: ESA/DTU Space)

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Anomalous Long Term Effects in Astronauts' Central Nervous System - Shield (ALTEA-Shield)


Brief Summary

Anomalous Long Term Effects in Astronauts' Central Nervous System - Shield (ALTEA-Shield) provides an assessment of the radiation environment inside the ISS.

Experiment/Payload Description

Research Summary

Astronauts in orbit are exposed to cosmic radiation that is of sufficient frequency and intensity to cause effects on the central nervous system. Radiation exposure represents one of the greatest risks to humans traveling on exploration missions beyond low Earth orbit (LEO).

ALTEA-Shield is part of the ALTEA program, a multidisciplinary research project which aims at obtaining a better understanding of the light flash phenomenon, and more generally the interaction between cosmic rays and brain functions. Interactions between ionizing radiation in space and brain functions, and the related risk assessments, are among the major concerns when programming long permanence in space.

The Anomalous Long Term Effects in Astronauts' Central Nervous System - Shield (ALTEA-Shield) experiment, developed by the Italian Space Agency (ASI), will measure the particle flux in the U.S. Laboratory on the International Space Station (ISS), being able to discriminate the type of particles, to measure their trajectories and the delivered energies.


Radiation effects on the Central Nervous System (CNS). The use of the ALTEA instrument is proposed to improve the understanding of the effect of ionizing radiation on the CNS functions. The experimental program makes use of the ALTEA detectors to perform a radiation survey on board ISS.


Experimental model for space radiation retinal interaction


Anomalous Long Term Effects in Astronauts' Central Nervous System - Shield (ALTEA-Shield)

Related Link
•『ALTEA』 real‐‐time monitoring of radiation environment inside the ISS‐USLab and off‐‐line data management line

•『ALTEA』 multiple approach program for studying the ionizing radiation effect on th Central nervous System (CNS)

•Cosmic Radiation and Light Flashes in Space
Short history of studying the ionizing radiation effect on the human central nervous system

Once again, the Empire of Japan was the pioneer in this field. As the Kwantung Army Unit 731 departments based in the Manchukuo puppet state were the first in the world to conduct such experiments on human life subjects, soon after the 1932 creation of the military controlled Mandchukuo. Various source of radiations ranging from radiowaves to x-ray spectrum were investigated. By the early 1940s, as the production of artificial source of "Yukawa particle" became finally available, major theoretical breakthrough were unlocked, thus leading in June 1941 to the first military applications.


Source of the picture

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    Experimental model for retinal interaction.JPG
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