Sprites form at plasma irregularities in Earth's lower ionosphere

This is a photograph of a sprite. 

Credit: H. H. C. Stenbaek-Nielsen

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.

Victor Pasko

"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.

Jianqi Qin

"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.

This is a photograph of five plasma irregularities responsible for sprite initiation. 

Credit: H. H. C. Stenbaek-Niels

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 (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.

This is a sequence of black and white images of sprite initiation on July 20, 2012. 

Credit: H. H. C. Stenbaek-Nielsen

ISS Image: Lightning Above the Middle East

This image of lightning over Kuwait was taken by an astronaut aboard the International Space Station on Dec. 12, 2013.

Credit: NASA Earth Observatory

This stunning image of a lightning strike over Kuwait was captured last December by an astronaut aboard the International Space Station (ISS) and released today (March 24) by NASA's Earth Observatory.

The ISS recently installed Firesation, a new instrument to help study the physics and composition of such bolts in detail on a daily basis.

Firesation being readied

Lightning bolts flash across Earth's atmosphere as often as 50 times per second, which adds up to about 4.3 million times a day and 1.5 billion times a year, NASA officials wrote in an image description.

Some of those strikes emit gamma radiation, a type of radiation more commonly associated with exploding stars and nuclear fusion, in bursts known as terrestrial gamma-ray flashes (TGFs).

The GLAST Burst Monitor (GBM), an instrument aboard NASA's Fermi Gamma-ray Space Telescope, was recently fine-tuned to better catch TGFs, and this allowed scientists to discover that TGFs also emit radio waves.

The scientists will use the new lightning imagery and data from the ISS to try to understand what triggers lightning during storms in general, and what causes these rarer bursts of TGFs

Doug Rowland

"The fact that TGFs exist at all is amazing," Doug Rowland, a space physicist at NASA's Goddard Space Flight Center involved in this new lighting research, said in a statement.

"The electron and gamma-ray energies in TGFs are usually the domain of nuclear explosions, solar flares, and supernovas."

"What a surprise to find them shooting out of the cold upper atmosphere of our own planet."

Researchers think these TGFs may be related to enigmatic red bursts of lightning called red sprites, which travel upward from thunderstorms and can take on ornate shapes that look like jellyfish.

Red sprites are just one of several types of lightning that researchers are still studying to understand their origin and structure.

In fact, lightning, in general, is a mysterious phenomenon, with scientists still not sure exactly how lightning forms.

The working hypothesis suggests it forms when an updraft of warm air reaches a height where the temperature is just above freezing; at this point, ice crystals and frozen particles interact with each other to produce an electric charge separation; when that separation becomes great enough an electrical breakdown occurs i.e. a lightning flash.

NASA leads NSF firefly mission to study lightning - Video

Somewhere across the Earth each day and night, there's a lightning flash. The globe experiences lightning some 50 times a second, yet the details of what initiates this common occurrence and what effects it has on the atmosphere – lightning may be linked to incredibly powerful and energetic bursts called terrestrial gamma ray flashes, or TGFs—remains a mystery.

Firefly, a milk-carton-sized satellite, will study gamma-ray bursts that accompany lightning.

Credit: Zina Deretsky, National Science Foundation

In mid-November, a football-sized mission called Firefly, which is funded by the National Science Foundation, will launch into space to study lightning and these gamma ray flashes from above.

The Firefly instrument is what's known as a cubesat, a very small satellite that offers the chance for quality space science with a relatively inexpensive price tag.

"We can do great science with these small missions," said Doug Rowland, the principal investigator for Firefly at NASA's Goddard Space Flight Center in Greenbelt, Md.

"Firefly will gather up to a year of observations on the mysterious workings of lightning. Lightning is so familiar we tend to take it for granted, but we really don't know the details of how it works—even though it is a critical part of the global electric circuit, and has obvious social and technological effects."

Lightning is ubiquitous and intimately connected to life on Earth, but we don't often think about what's happening higher up in the atmosphere.

The radiation generated by lightning is so intense that it can generate antimatter and gamma rays within TGFs just a few miles of the ground.

NASA's Compton Gamma Ray Observatory first discovered TGFs in the 1990s. Designed to look outward at cosmic sources of gamma rays, the mission also caught rare but tantalizing glimpses of gamma rays coming from Earth.

This is an artist's rendition of the football-sized Firefly satellite in low-Earth orbit. 

Firefly's mission is to study the relationship between lightning and huge bursts of gamma rays called terrestrial gamma ray flashes. 

Credit: NASA/Goddard Space Flight Center

Russian researchers find more evidence that lightning is caused by cosmic rays

Russian physicists Alex Gurevich and Anatoly Karashtin claim, in a paper published in the journal Physical Review Letters, they have found more evidence to support their idea that lightning is caused by cosmic rays.

The notion was first proposed by Gurevich back in 1992, and has been a source of debate ever since.

No one really knows what causes lightning to form and strike—the prevailing view is that it comes about as a result of collisions between ice crystals in clouds and hail stones. But because clouds and the lightning they produce are unpredictable and hard to pin down, no one has been able to prove this theory.

Another theory, proposed by Gurevich twenty years ago, says that lightning is formed from the collisions between cosmic rays and water droplets present in thunderclouds. Now he and a colleague claim to have found evidence to support this idea.

Gurevich suggests that cosmic rays entering thunder clouds cause the air in them to be ionized, resulting in a lot of free electrons floating around. The electronic field already present in the cloud, he continues, leads to the free electrons being boosted to higher energies.

When the electrons present in the air collide with water atoms, more electrons are released, setting off what he describes as an avalanche of high-energy particles that eventually give way to a "runaway breakdown"—a discharge that is witnessed as a lightning strike.

As with other theories regarding the origins of lightning, Gurevich's ideas haven't been proved. But he hasn't been sitting still.

In this new effort, he along with Karashtin have been measuring and analyzing radio waves in storm clouds as lightning occurs. The idea is that if such strikes are due to interactions with cosmic rays, there should be measurable amounts of radio waves given off.

Gurevich and Karashtin set up equipment to monitor storm clouds over Russia and Kazakhstan—recording radio waves emitted during 3,800 lightning strikes. In analyzing the data, they found that hundreds, and perhaps even thousands of short radio wave pulses occurred just as a bolt of lightning was about to form.

Perhaps more importantly, they matched the models Gurevich had built years before. There was on hitch however, the amount of energy delivered by the cosmic rays in the model don't happen often enough in the real world to cause lightning strikes in most every thunderstorm.

Gurevich and Karashtin say the discrepancy can be explained by the addition of energy into the system by free electrons passing near hydrometeors (bits of hail or water droplets).

When that happens, very small discharges result, adding to the total charge. Taken together they say, enough energy is added to cause the cascade that leads to lightning formation.

More information: Runaway Breakdown and Hydrometeors in Lightning Initiation, Phys. Rev. Lett. 110, 185005 (2013). prl.aps.org/abstract/PRL/v110/i18/e185005

Whiplash Lightning, Munich, Germany

A whiplash-shaped lightning bolt illuminates the night sky above the skyline of Munich, southern Germany

Picture: PETER KNEFFEL/AFP/GettyImages

NASA ISS Crew seeing elusive Cosmic Sprites - Rare Video

A sprite glows red (inset) in this image captured by astronauts on the International Space Station on April 30, 2012.   

Credit: Image Science & Analysis Laboratory, NASA Johnson Space Center 

High above the clouds during thunderstorms, some 50 miles above Earth a different kind of lightning dances.

Bursts of red and blue light, known as "sprites," flash for a scant one thousandth of a second. They are often only visible to those in flight above a storm, and happen so quickly you might not even see it unless you chance to be looking directly at it.

One hard-to-reach place that gets a good view of sprites is the International Space Station. On April 30, 2012, astronauts on the ISS captured the signature red flash of a sprite, offering the world and researchers a rare opportunity to observe one.

Filmed at 10,000 frames per second by Japan's NHK television, movies like this of electromagnetic bursts called "sprites" will help scientists better understand how weather high in the atmosphere relates to weather on the ground. 

Credit: NHK

Indeed, sprites are so hard to catch on film, that pilots had claimed to see them for almost a century before scientists at the University of Minnesota accidentally caught one on camera in July of 1989.

Since then, researchers aboard planes have occasionally snapped a shot, but it continues to be difficult to methodically film them.

So a group of scientists, along with help from Japan's NHK television, sought them out regularly for two weeks in the summer of 2011.

Filming at 10,000 frames per second on two separate jets, the team recorded some of the best movies of sprites ever taken – movies that can be used to study this poorly understood phenomenon and the forces that create them.

By filming from two jets flying 12 miles apart, the team mapped out the 3-dimensional nature of the sprites. Ground-based measurements rounded out the picture.

NASA Cassini Image: Lightning on Saturn

These false colour mosaics from NASA's Cassini spacecraft capture lightning striking within the huge storm that encircled Saturn's northern hemisphere for much of 2011. 

For a larger version of this image please go here.
 

Saturn was playing the lightning storm blues.

NASA's Cassini spacecraft has captured images of last year's storm on Saturn, the largest storm seen up-close at the planet, with bluish spots in the middle of swirling clouds.

Those bluish spots indicate flashes of lightning and mark the first time scientists have detected lightning in visible wavelengths on the side of Saturn illuminated by the sun.

"We didn't think we'd see lightning on Saturn's day side - only its night side," said Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology in Pasadena. "The fact that Cassini was able to detect the lightning means that it was very intense."

The storm occurred last year. The lightning flashes appear brightest in the blue filter of Cassini's imaging camera on March 6, 2011. Scientists aggressively heightened the blue tint of the image to determine its size and location.

Scientists are still analysing why the blue filter catches the lightning. It might be that the lightning really is blue, or it might be that the short exposure of the camera in the blue filter makes the short-lived lightning easier to see.

What scientists do know is that the intensity of the flash is comparable to the strongest flashes on Earth. The visible energy alone is estimated to be about 3 billion watts lasting for one second.

The flash is approximately 100 miles (200 kilometers) in diameter when it exits the tops of the clouds. From this, scientists deduce that the lightning bolts originate in the clouds deeper down in Saturn's atmosphere where water droplets freeze. This is analogous to where lightning is created in Earth's atmosphere.

In composite images that show the band of the storm wrapping all the way around Saturn, scientists have seen multiple flashes. In one composite image, they recorded five flashes, and in another, three flashes.

"As summer storm season descends upon Earth's northern latitudes, Cassini provides us a great opportunity to see how weather plays out at different places in our solar system," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"Saturn's atmosphere has been changing over the eight years Cassini has been at Saturn, and we can't wait to see what happens next."

NASA Shuttle Image: Lightning flashes, city lights, sunset, Aurora Australis

Lightning flashes, city lights, sunset, Aurora Australis, atmospheric glow and some stars, seen over Argentina on 4/23/2003

Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center

Lightning Strikes The Golden Gate Bridge, San Francisco - Image

All Credit to photographer Phil McGrew for this remarkable shot.

Fabulous Picture of 'strange looking rocks'

After months of anticipation and exhausting preparations and planning for taking photos of the total lunar eclipse, everything went wrong due to a severe thunderstorm during the phenomenon.

Everything? Well...fortunatelly no, because for approximately 10 minutes in the middle of totality, a small window in the sky allowed me to see the Moon in the Earth's shadow and shoot this unbelievable photo.

The shot was taken from Ikaria island at Pezi, an area known as "the planet of the goats", because of the rough terrain with the strange looking rocks

Rocket-triggered lightning in Florida

This University of Florida image shows rocket-triggered lightning at the UF/FIT International Centre for Lightning research and Testing near Gainsville, Florida.

Researchers for the first time have captured X-ray images of lightning, a feat that they hope will help them better predict how lightning moves.

A team from the Florida Institute of Technology and University of Florida launched small rockets into thunderclouds.

Using a special camera, the researchers recorded X-rays coming from the resulting light flashes before they hit the ground. Scientists have known that lightning emits X-rays, but they don't fully understand it.

Picture: AP / UNIVERSITY OF FLORIDA

Lightning Strikes Statue of Liberty

A lightning bolt appears to strike the Statue of Liberty. The moment was captured by New York photographer Jay Fine who spent the night braving the storm in Battery Park City, Manhattan, in a bid to get the perfect picture.

Jay spent nearly two hours poised with his camera and took more than 80 shots before striking lucky with this particular bolt of lightning at 8.45pm on September 22
Picture: JAY FINE / CATERS NEWS

Lightning filmed at 9,000 frames per second – Telegraph Blogs

Tom A Warner has filmed lightning in slow motion at an astonishing frame rate of 9,000 images per second. When slowed down like this the forks snake across the sky properly, just as you always thought they should if only your eye could keep up.

A Great Image of the awesome prower of Lightning: MIKE HOLLINGSHEAD

Spectacular shot of the North Omaha Tower being 'struck' by lightning. In fact, those bolts are going upwards, off the towers.

Masts and aerials are a common target in lightning storms and this group were 'struck' at least five times in 15 minutes.

The second picture shows more lightning strikes at the North Omaha tower.

You can see more of Mike's work on his website

Credit Picture: MIKE HOLLINGSHEAD / SOLENT

Lightning Jets and Sprites

The ancient Greeks might have thought Zeus was furious with heaven itself. The power of lightning strikes and Sprites, that shoot upwards from storm clouds has been measured for the first time – and they turn out to be every bit as powerful as normal lightning.

First caught on camera in 2003, "gigantic jets" shoot upwards from thunderclouds and can reach altitudes above 80 kilometres. But it wasn't until 21 July last year that Steven Cummer at Duke University in Durham, North Carolina, and his colleagues managed to measure the electrical discharge from a single gigantic jet, released from tropical storm Cristobal.

"No one had been very close to one with the right radio instrumentation before," Cummer says. "So we didn't know whether they just petered out without doing anything much, or whether they actually took some charge and dumped it somewhere."