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

Turkey's Controversial Reform Bill Giving Investors Jitters

Homeland security reform bill will give police new powers in search, seizure, detention and arrests, while restricting the rights of suspects, their attorneys More

Audio Slideshow In Kenyan Prison, Good Grades Are Path to Freedom

Some inmates who get high marks could see their sentences commuted to non-custodial status More

'Rumble in the Jungle' Turns 40

'The Champ' knocked Foreman out to regain crown he had lost 7 years earlier when US government accused him of draft-dodging and boxing officials revoked his license More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Victorious Secularists Face Challenge to Form Government in Tunisiai
X
Henry Ridgwell
October 30, 2014 11:39 PM
Official results from Tunisia show the Islamist Ennahda party has failed to win the second free election since the so-called "Arab Spring" uprising in 2011. Ennahda, which handed power to a government of technocrats pending the elections, lost out to the secular party Nidaa Tounes. Henry Ridgwell reports from London that the relatively peaceful poll offers some hope in a volatile region.
Video

Video Victorious Secularists Face Challenge to Form Government in Tunisia

Official results from Tunisia show the Islamist Ennahda party has failed to win the second free election since the so-called "Arab Spring" uprising in 2011. Ennahda, which handed power to a government of technocrats pending the elections, lost out to the secular party Nidaa Tounes. Henry Ridgwell reports from London that the relatively peaceful poll offers some hope in a volatile region.
Video

Video Africa Tells its Story Through Fashion

In Africa, Fashion Week is a riot of colors, shapes, patterns and fabrics - against the backdrop of its ongoing struggle between nature and its fast-growing urban edge. How do these ideas translate into needle and thread? VOA’s Anita Powell visited this year’s Mercedes Benz Fashion Week Africa in Johannesburg to find out.
Video

Video Smugglers Offer Cheap Passage From Turkey to Syria

Smugglers in Turkey offer a relatively cheap passage across the border into Syria. Ankara has stepped up efforts to stem the flow of foreign fighters who want to join Islamic State militants fighting for control of the Syrian border city of Kobani. But porous borders and border guards who can be bribed make illegal border crossings quite easy. Zlatica Hoke has more.
Video

Video China Political Meeting Seeks to Improve Rule of Law

China’s communist leaders will host a top level political meeting this week, called the Fourth Plenum, and for the first time in the party’s history, rule of law will be a key item on the agenda. Analysts and Chinese media reports say the meetings could see the approval of long-awaited measures aimed at giving courts more independence and include steps to enhance an already aggressive and high-reaching anti-corruption drive. VOA’s Bill Ide has more from Beijing.
Video

Video After Decades of Pressure, Luxembourg Drops Bank Secrecy Rules

European Union finance ministers have reached a breakthrough agreement that will make it more difficult for tax cheats to hide their money. The new legislation, which had been blocked for years by countries with a reputation as tax havens, was approved last week after Luxembourg and Austria agreed to lift their vetoes. But as Mil Arcega reports, it doesn’t mean tax cheats have run out of places to keep their money hidden.
Video

Video Kobani Refugees Welcome, Turkey Criticizes, US Airdrop

Residents of Kobani in northern Syria have welcomed the airdrop of weapons, ammunition and medicine to Kurdish militia who are resisting the seizure of their city by Islamic State militants. The Turkish government, however, has criticized the operation. VOA’s Scott Bobb reports from southeastern Turkey, across the border from Kobani.

All About America

AppleAndroid