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

Koreas Mark 61st Anniversary of War Armistice

Muted observances on both sides of heavily-armed Demilitarized Zone that separates two decades-long enemies More

Judge Declares Washington DC Ban on Public Handguns Unconstitutional

Ruling overturns capital city's prohibition on carrying guns in pubic More

Pricey Hepatitis C Drug Draws Criticism

Activists are using the International AIDS Conference to criticize drug companies for charging high prices for life-saving therapies More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Students in Business for Themselvesi
X
Mike O'Sullivan
July 26, 2014 11:04 AM
They're only high school students, but they are making accessories for shoes, fabricating backpacks and doing product photography - all through their own businesses. It's the result of a partnership between a non-profit organization that teaches entrepreneurship and their schools. VOA's Mike O'Sullivan and Deyane Moses met the budding entrepreneurs near Los Angeles.
Video

Video Students in Business for Themselves

They're only high school students, but they are making accessories for shoes, fabricating backpacks and doing product photography - all through their own businesses. It's the result of a partnership between a non-profit organization that teaches entrepreneurship and their schools. VOA's Mike O'Sullivan and Deyane Moses met the budding entrepreneurs near Los Angeles.
Video

Video Astronauts Train in Underwater Lab

In the world’s only underwater laboratory, four U.S. astronauts train for a planned visit to an asteroid. The lab - called Aquarius- is located five kilometers off Key Largo, in southern Florida. Living in close quarters and making excursions only into the surrounding ocean, they try to simulate the daily routine of a crew that will someday travel to collect samples of a rock orbiting far away from earth. VOA’s George Putic has more.
Video

Video Not Even Monks Spared From Thailand’s Junta-Backed Morality Push

With Thailand’s military government firmly in control after May’s bloodless coup, authorities are carrying out plans they say are aimed at restoring discipline, morality and patriotism to all Thais. The measures include a crackdown on illegal gambling, education reforms to promote students’ moral development, and a new 24-hour phone hotline for citizens to report misbehaving monks. Steve Sandford reports from Bangkok.
Video

Video Virtual Program Teaches Farming Skills

In a fast-changing world beset by unpredictable climate conditions, farmers cannot afford to ignore new technology. Researchers in Australia are developing an online virtual world program to share information about climate change and more sustainable farming techniques for sugar cane growers. As VOA's Zlatica Hoke reports, the idea is to create a wider support network for farmers.
Video

Video Airline Expert: Missile will Show Signature on Debris

The debris field from Malaysia Airlines Flight 17 is spread over a 21-kilometer radius in eastern Ukraine. It is expected to take investigators months to sort through the airplane pieces to learn about the missile that brought down the jetliner and who fired it. VOAs Carolyn Presutti explains how this work will be done.
Video

Video Treatment for Childhood Epilepsy Heats up Medical Marijuana Debate

In the United States, marijuana is classed as an illegal drug by the federal government. But nearly half the states have legalized it, to some degree. Proponents say some strains of marijuana might have exceptional health benefits, for treating pain or inflammation in chronic conditions such as cancer, multiple sclerosis and epilepsy. Shelley Schlender reports on a strain of medical marijuana developed in Colorado that is reputed to reduce seizures in childhood epilepsy
Video

Video Airbus Adds Metal 3D Printed Parts to New Jets

By the end of this year, European aircraft manufacturing consortium Airbus plans to deliver the first of its new, extra-wide-body passenger jets, the A350-XWB. Among other technological innovations, the new plane will also incorporate metal parts made in a 3-D printer. VOA's George Putic has more.
Video

Video AIDS Conference Welcomes Exciting Developments in HIV Treatment, Prevention

Significant strides have been made in recent years toward the treatment and prevention of HIV, the virus that causes AIDS. This year, at the International AIDS Conference, the AIDS community welcomed progress on a new pill that may prevent transmission of the deadly virus. VOA’s Anita Powell reports from Melbourne, Australia.
Video

Video IAEA: Iran Turns its Enriched Uranium Into Less Harmful Form

Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.

AppleAndroid