News / Science & Technology

Thunderstorms Generate Mysterious 'Dark Lightning'

This NOAA satellite image shows shower and thunderstorm activity developing around an area of low pressure spinning in the Gulf of Mexico, June 23, 2012.
This NOAA satellite image shows shower and thunderstorm activity developing around an area of low pressure spinning in the Gulf of Mexico, June 23, 2012.
Rick Pantaleo
Have you ever heard of "dark lightning?"  Few people outside the scientific community have, but it is something real that is actually quite powerful - and possibly dangerous.  A group of scientists in Florida has been learning about this mysterious natural phenomenon:

We all know what thunderstorms are, and how much havoc their violent winds, torrential rains and lightning strikes can cause.  But over the past 10 years, scientists have learned of an even darker side to thunderstorms: they can generate powerful bursts of electromagnetic energy known as Terrestrial Gamma-Ray Flashes, or TGFs.
 
“A few years back, a spacecraft started seeing these bursts of gamma rays coming up from the Earth’s atmosphere," said Joseph Dwyer. "It was very strange.  The Earth is not supposed to make gamma rays.  If you want to study gamma rays you usually look for places like black holes and supernovas.  We figured out eventually that these gamma rays were coming from ordinary thunderstorms.”

Professor Joseph Dwyer and his colleagues at the Florida Institute of Technology have been researching so-called “dark lightning” for several years.  Dwyer says that while the phenomenon is quite different from what we see flashing brightly in the sky during a thunderstorm, the two types of high-energy events can be produced by the same storms, but in different ways.

“Normal lightning is very hot," he said. "It’s about five times as hot as the surface of the sun and because of that emits a lot of light.  But, compared to the gamma ray energy scale, it’s downright cold.  So normal lightning is not hot enough to make the kind of gamma rays we’ve been seeing and so we needed some other explanation.  What we now think is going on is that a thunderstorm acts like a gigantic particle accelerator.  Strong fields inside the thunderstorm accelerate electrons to almost the speed of light and then they make the gamma-rays.”

A tremendous amount of energy is released in dark lightning, yet its powerful discharge is silent, and almost completely invisible to the unaided eye.

Scientists have been concerned  that since these gamma-ray bursts can originate at the same altitudes where commercial aircraft fly, they could damage the planes and jeopardize the safety of airline passengers. But Dwyer points to a couple of factors that minimize those dangers.

“First of all, pilots do their best to stay away from thunderstorms," said Dwyer. "Thunderstorms are dangerous places; we all know that already, so no additional warning is needed.  And the second piece of good news is dark lightning appears to be relatively rare, maybe one out of every thousand normal lightning flashes would be dark lightning.  So combining those two, people should not be worrying about this.”

Dwyer notes that astronauts peering down from Earth-orbiting spacecraft have reported that these gamma-ray producing storms occur most often around the equatorial regions of the planet.  Dwyer says that could be because storms in those areas tend to be taller, higher-altitude thunderstorms, so their gamma-rays are bursting closer to space - and more visibly to the astronauts - since there’s less atmosphere for the light to pass through.
 
Dwyer says that in general, any thunderstorm should be capable of generating dark lightning. He says he and his colleagues are still not certain what’s happening inside a thunderstorm that makes one storm more likely than another to generate the gamma-ray discharges, so more research on dark lightning is needed.
 
“It would be very nice to have instruments that were specifically designed to measure what we’re interested in studying," he said. "Now, we’re talking about something that’s happening right over our heads that could affect people, that may be relatively common and so it would be very interesting to learn more about this.”  

The researchers say new data from special Earth-observing satellites will help them better understand dark lightning.  And while studies of the phenomenon continue, Professor Dwyer’s research has found no evidence yet that the mysterious gamma-ray bursts in thunderstorms pose any direct threat to public health or the environment.

You May Like

At International AIDS Conference One Goal, Many Paths

The 12,000 delegates attending 20th International AIDS Conference in Melbourne have vastly different visions about how to eradicate disease More

Disasters May Doom Malaysia’s Flag Carrier

Even before loss of two jets loaded with passengers on international flights, company had been operating in red for three years, accumulating deficit of $1.3 billion More

Afghan Presidential Vote Audit Continues Despite Glitches

Process has been marred by walkouts by representatives of two competing candidates, Abdullah Abdullah and Ashraf Ghani More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Nature of Space Exploration Enters New Agei
X
Elizabeth Lee
July 20, 2014 2:36 AM
Forty-five years ago this month, the first humans walked on the moon. It was during an era of the space race between the United States and the Soviet Union. World politics have changed since then and -- as Elizabeth Lee reports -- so has the nature of space exploration.
Video

Video Nature of Space Exploration Enters New Age

Forty-five years ago this month, the first humans walked on the moon. It was during an era of the space race between the United States and the Soviet Union. World politics have changed since then and -- as Elizabeth Lee reports -- so has the nature of space exploration.
Video

Video Chicago’s Argonne Lab Developing Battery of the Future

In 2012, the U.S. Department of Energy’s Office of Science awarded a $120 million grant to a new technology center focused on battery development - headquartered at Argonne National Laboratory in suburban Chicago, Illinois. As VOA’s Kane Farabaugh reports, there scientists are making the next technological breakthroughs in energy storage.
Video

Video In NW Pakistan, Army Offensive Causes Massive Number of Displaced

Pakistan’s army offensive in North Waziristan has resulted in the large-scale displacement of the local population. VOA's Ayaz Gul reports from northwest Pakistan where authorities say around 80 percent of the estimated 1 million internally displaced persons [IDPs] have settled in Bannu district, while much of the remaining 20 percent are scattered in nearby cities.
Video

Video Kurdish Peshmerga Force Secures Kirkuk, Its Oil

The Kurdistan regional government has sent its Peshmerga troops into the adjacent province of Kirkuk to drive out insurgents, and to secure the area's rich oil fields. By doing this, the regional government has added a fourth province to the three it officially controls. The oil also provides revenue that could make an independent Kurdistan economically strong. VOA’s Jeffrey Young went out with the Peshmerga and filed this report.
Video

Video Malaysia Reeling: Second Air Disaster in Four Months

Malaysia is reeling from the second air disaster in four months involving the country’s flag carrier. Flight 340 vanished in March and despite an extensive search, no debris has been found. And on Thursday, Flight 17, likely hit by a surface-to-air missile, came apart over eastern Ukraine. The two incidents together have left more than 500 people dead. VOA Correspondent Steve Herman reports from Kuala Lumpur.
Video

Video Diplomatic Crisis Grows Over MH17 Plane Crash

The Malaysia Airlines crash in eastern Ukraine is drawing reaction from leaders around the world. With suspicions growing that a surface-to-air missile shot down the aircraft, there are increasing tensions in the international community over who is to blame. Henry Ridgwell reports for VOA from London.
Video

Video Undocumented Immigrants Face Perilous Journey to US, No Guarantees

Every day, hundreds of undocumented immigrants from Central America attempt the arduous journey through Mexico and turn themselves over to U.S. border patrol -- with the hope that they will not be turned away. But the dangers they face along the way are many, and as Ramon Taylor reports from the Rio Grande Valley in Texas, their fate rests on more than just the reception they get at the US border.
Video

Video Scientists Create Blackest Material Ever

Of all the black things in the universe only the infamous "black holes" are so black that not even a tiny amount of light can bounce back. But scientists have managed to create material almost as black, and it has enormous potential use. VOA’s George Putic has more.
Video

Video Fog Collector Transforming Maasai Water Harvesting in Kenya

The Maasai people of Kenya are known for their cattle-herding, nomadic lifestyle. But it's an existence that depends on access to adequate water for their herds and flocks. Lenny Ruvaga reports for VOA, on a "fog collector."

AppleAndroid