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

How to Safeguard Your Mobile Privacy

As the digital world becomes more mobile, so too do concerns about eroding privacy and increased hacking More

'Desert Dancer' Chronicles Iranian Underground Dance Troupe

Film by Richard Raymond is based on true story of Afshin Ghaffarian and his friends More

Obesity Poses Complex Problem

Professor warns of obesity’s worldwide health impact More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam Wari
X
Katherine Gypson
May 25, 2015 1:32 AM
For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.
Video

Video Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam War

For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.
Video

Video Female American Soldiers: Healing Through Filmmaking

According to the United States Defense Department, there are more than 200-thousand women serving in the U.S. Armed Forces.  Like their male counterparts, females have experiences that can be very traumatic.  VOA's Bernard Shusman tells us about a program that is helping some American women in the military heal through filmmaking.
Video

Video Iowa Family's Sacrifice Shaped US Military Service for Generations

Few places in America have experienced war like Waterloo. This small town in the Midwest state of Iowa became famous during World War II not for what it accomplished, but what it lost. As VOA’s Kane Farabaugh reports, the legacy of one family’s sacrifice is still a reminder today of the real cost of war for all families on the homefront.
Video

Video On Film: How Dance Defies Iran's Political Oppression

'Desert Dancer' by filmmaker Richard Raymond is based on the true story of a group of young Iranians, who form an underground dance troupe in the Islamic Republic of Iran. This is the latest in a genre of films that focus on dance as a form of freedom of expression against political oppression and social injustice. VOA’s Penelope Poulou has more.
Video

Video Turkey's Ruling Party Trying to Lure Voters in Opposition Stronghold

Turkey’s AK (Justice and Development) Party is seeking a fourth successive general election victory, with the goal of securing two-thirds of the seats in Parliament to rewrite the constitution and change the country's parliamentary system into a presidential one. To achieve that, the party will need to win seats in opposition strongholds like the western city of Izmir. Dorian Jones reports.
Video

Video Millions Flock to Ethiopia Polls

Millions of Ethiopians cast their votes Sunday in the first national election since the 2012 death of longtime leader Meles Zenawi. Mr. Meles' party, the Ethiopian People's Revolutionary Democratic Front, is almost certain of victory again. VOA's Anita Powell reports from Addis Ababa.
Video

Video Scientists Testing Space Propulsion by Light

Can the sun - the heart of our solar system - power a spacecraft to the edge of our solar system? The answer may come from a just-launched small satellite designed to test the efficiency of solar sail propulsion. Once deployed, its large sail will catch the so-called solar wind and slowly reach what scientists hope to be substantial speed. VOA’s George Putic reports.
Video

Video FIFA Trains Somali Referees

As stability returns to the once lawless nation of Somalia, the world football governing body, FIFA, is helping to rebuild the country’s sport sector by training referees as well as its young footballers. Abdulaziz Billow has more from Mogadishu.
Video

Video With US Child Obesity Rates on the Rise, Program Promotes Health Eating

In its fifth year, FoodCorps puts more than 180 young Americans into 500 schools across the United States, where they focus on teaching students about nutrition, engaging them with hands-on activities, and improving their access to healthy foods whether in the cafeteria or the greater community. Aru Pande has more.
Video

Video Virginia Neighborhood Draws People to Nostalgic Main Street

In the U.S., people used to grow up in small towns with a main street lined by family-owned shops and restaurants. Today, however, many main streets are worn down and empty because shoppers have been lured away by shopping malls. But in the Del Ray neighborhood of Alexandria, Virginia, main street is thriving. VOA’s Deborah Block reports it has a nostalgic feel with its small restaurants and unique stores.

VOA Blogs