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

Analyst: Joint-Arab Military Force Poses Perilous Challenge

Although international forces are desperately needed to counter the threat of the Islamic State group, analysts say conflicting alliances could escalate fighting More

Asia’s Middle Class Changes Demand for Wheat Grain Exporters

Changes in tastes and diets are boon for wheat exporters such as Australia and the United States More

S. African Comedian Taking Over Popular TV Show

Mixed-race comedian Trevor Noah, who is loved for his edgy jibes about race and language, is taking the helm from Jon Stewart at The Daily Show in US More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Film Tells Story of Musicians in Mali Threatened by Jihadistsi
X
Greg Flakus
March 30, 2015 6:48 PM
At this year's annual South by Southwest film and music festival in Austin, Texas, some musicians from Mali were on hand to promote a film about how their lives were upturned by jihadists who destroyed ancient treasures in the city of Timbuktu and prohibited anyone from playing music under threat of death. As VOA’s Greg Flakus reports from Austin, some are afraid to return to their hometowns even though the jihadists are no longer in control there.
Video

Video Film Tells Story of Musicians in Mali Threatened by Jihadists

At this year's annual South by Southwest film and music festival in Austin, Texas, some musicians from Mali were on hand to promote a film about how their lives were upturned by jihadists who destroyed ancient treasures in the city of Timbuktu and prohibited anyone from playing music under threat of death. As VOA’s Greg Flakus reports from Austin, some are afraid to return to their hometowns even though the jihadists are no longer in control there.
Video

Video With Coalition Airstrikes, Iraq Entering 'Last Page' of IS Battle

American warplanes joined Iraq's battle against the so-called 'Islamic State' in northern Iraq late Wednesday, as Iraqi ground troops launched a massive assault on Tikrit. Analysts say the offensive could take the coalition a step further towards Mosul, the largest city held by Islamic State forces. Others say it could also deepen already-dangerous sectarian tensions in the region. VOA's Heather Murdock has more from Cairo.
Video

Video Philippines Wants Tourists Spending Money at New Casinos

Tourism is a multi-billion dollar industry in the Philippines. Close to five million foreign visitors traveled there last year, perhaps lured by the country’s tropical beaches. But Jason Strother reports from Manila that the country hopes to entice more travelers to stay indoors and spend money inside new casinos.
Video

Video Civilian Casualties Push Men to Join Rebels in Ukraine

The continued fighting in eastern Ukraine and the shelling of civilian neighborhoods seem to be pushing more men to join the separatist fighters. Many of the new recruits are residents of Ukraine made bitter by new grievances, as well as old. VOA's Patrick Wells reports.
Video

Video Islamic State Prisoners Talk of Curiosity, God, Regret

Islamic State fighter, a prisoner of Kurdish YPG forces, asked his family asking for forgiveness: "I destroyed myself and I destroyed them along with me." The Syrian youth was one of two detainees who spoke to VOA’s Kurdish Service about the path they chose; their names have been changed and identifying details obscured. VOA's Zana Omer reports.
Video

Video Germanwings Findings Raise Issue of Psychological Testing for Pilots

More is being discovered about the co-pilot in the crash of Germanwings Flight 9525 in the French Alps. Investigators say he was hiding a medical condition, raising questions about the mental qualifications of pilots. VOA's Carolyn Presutti reports.
Video

Video Hi-tech Motorbike Helmet's Goal: Improve Road Safety

In cities with heavily congested traffic, people can get around much faster on a motorcycle than in a car. But a rider who is not sure of his route may have to stop to look at the map or consult a GPS. A Russian start-up company is working to make navigation easier for motorcyclists. Designers at Moscow-based LiveMap are developing a smart helmet with a built-in navigation system, head-mounted display and voice recognition. Zlatica Hoke has more.
Video

Video DOJ: Illinois National Guard Soldier Tried to Join ISIS

U.S. federal law enforcement agents arrested two suburban Chicago men accused of trying to join ISIS overseas, while also plotting attacks in the United States. As VOA’s Kane Farabaugh reports from the Midwest state of Illinois, one of those arrested is a soldier of the Illinois National Guard.
Video

Video New Wheelchair Is Easier to Use, Increases Mobility

Traditional push-rim wheelchairs create a lot of stress for arm, shoulder and neck muscles and joints. A redesigned chair, based on readily available bicycle technology, radically increases mobility while reducing the physical effort. VOA’s George Putic reports.
Video

Video Liberia's Almost Last Ebola Patient Grateful but Still Grieving

Beatrice Yardolo was to make history as Liberia’s last Ebola patient. Liberians recently started counting down 42 days, the period that has to go by without a single new infection until the World Health Organization can declare a country Ebola-free. That countdown stopped on March 20 when there was another new case of Ebola, making Yardolo’s story a reminder that Ebola is far from over. Benno Muchler reports from Monrovia.
Video

Video Cambodian Land Grabs Threaten Traditional Communities

Indigenous communities in Cambodia's Ratanakiri province say the government’s economic land concession policy is taking away their land and traditional way of life, making many fear that their identity will soon be lost. Local authorities, though, have denied this is the case. VOA's Say Mony went to investigate and filed this report, narrated by Colin Lovett.
Video

Video Space Program Status Disappoints 'Last Man on the Moon'

One of the films that drew big crowds last week at the annual South by Southwest festival in Austin, Texas, tells the story of the last human being to stand on the moon, U.S. astronaut Eugene Cernan. It has been 42 years since Cernan returned from the moon and he laments that no one else has gone there since. VOA’s Greg Flakus reports.

VOA Blogs

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More