The Mysteries of Dark Lightning

The pursuit for the understanding of the world around us is one of man’s greatest obsessions. Entire fields of study have been formed to explain everything from the inner workings of tiny particles to the awesome power of phenomena such as storms and lightning. There are those among us that build their careers on finding the reason ‘why’ things behave the way they do. These are the fearless, the bold, and maybe just a little bit crazy research scientists.

XKCD's Depiction of Scientific Curiosity

 

One such group of scientists from the Florida Institute of Technology, led by Joseph Dwyer, is studying a newly observed type of lightning called ‘dark lightning’ or terrestrial gamma-ray flashes (TGFs). Currently there are conflicting opinions about the specific properties of dark lightning. What is not disputed is that this type of wave exists and it is one of the most powerful energy forms composed of light that scientists have observed here on Earth. 

First a brief explanation of visible lightning

Lightning is nature’s way of equalizing the polarization between two clouds, within a single cloud, or between a cloud and the surface of the Earth. As the electric field within a cloud increases, the air around the cloud begins to ionize. That is, electrons are pulled away from the surrounding air molecules. These fragments of molecules form a conductive plasma pathway between two objects. The positive ions travel upward through this path and the negative ions (electrons) travel downward. When they meet, a complete pathway is formed. Lightning is the result of the charge transfer between cloud and cloud or cloud and ground through that pathway.

Basic Principles of Visible Lightning

So exactly what is dark lightning and how is it related to regular lightning?

Periodically energy outbursts are observed in high energy thunderstorms. The theory is that certain conditions cause the electric field built up by the storm to discharge in a different way. Storms can discharge energy by converting it into a flash of intense ionizing (x-rays and gamma rays) radiation that travels upward rather than channeling that energy downward in the form of heat and light. These waves are radiated upward in all directions instead of formed into a directed bolt. As such, this cloud of energy dissipates quickly.

(From left to right) Start of energy transferal, energy discharged up as 'dark lightning', energy discharged down as visible lightning (Credit: Studio Gohde)

Gamma rays? Those are only man-made or found around black holes and supernovas right? 

Scientists previously assumed that this was the case.  After some extensive research, Professor Dwyer and his team have a theory that the thunderstorm acts as a giant particle accelerator. Electrons are accelerated almost to the speed of light by the strong electrical fields in the storm.  More study is needed to define the method of generation and properties of this phenomenon. The advantage to further research in this field is that there are many devices already designed that detect and analyze gamma radiation.

Is dark lightning dangerous to humans?

Any kind of ionizing radiation is harmful to humans on some level. However, the likelihood of being close enough to absorb enough rays to be harmed is pretty slim. Dark lightning occurs in the neighborhood of 16,000 feet. Commercial airplanes cruise at an altitude of about 30,000 to 40,000 feet so at most the plane would pass through the height in question twice during their flight. Also pilots try to avoid flying through the heart of a thunderstorm.  Even if the timing was just right, the amount of radiation emitted by a flash of dark lightning is maybe up to the equivalent of 10 chest X-rays around the edges and up to 1 full-body CT scan in the very center of the radiation burst according to research scientist, Joseph Dwyer. Dwyer also indicated that dark lightning seems to be fairly rare; he and his team have figured that dark lightning occurs maybe once for every thousand visible lightning flashes.

So next time a storm rolls in, think about all of the amazing properties that come along with that storm. This discovery shows just how much exploring we have to do even in our own backyards. Imagine what future generations of research scientists will find.

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D-tect Systems is a supplier of advanced radiation and chemical detection equipment sold around the world. www.dtectsystems.com.

References:

Thunderstorms Generate Mysterious 'Dark Lightning', Rick Pantaleo, voanews.com

http://www.voanews.com/content/thunderstorms-generate-mysterious-dark-lightning/1652547.html

Dark Lightning Linked to its Luminous Twin, Becky Oskin, Live Science

http://www.livescience.com/29019-dark-lightning-linked-visible-lightning.html

Scientists detect dark lightning linked to visible lightning, Nikolai Østgaard, AGU

http://www.agu.org/news/press/pr_archives/2013/2013-15.shtml

Florida Institute of Technology

http://gpl.fit.edu/Overview.htm

Wikipedia (Overview of Lightning)

http://en.wikipedia.org/wiki/Lightning

Deciphering Hazmat Symbols

Have you ever wondered what those large tanker trucks are carrying? How do you know if a given truck is carrying anything radioactive? Would the truck be glowing green like in cartoons?

Radioactive Cartoon Truck

While fun to think about, radioactive materials can’t be identified in such an obvious way. However there is a labeling standard detailed by the US Department of Transportation (DOT) that requires trucks to post what type of material they are carrying. The label found on these trucks is a symbol in a colored diamond. These signs may seem really cryptic but they can tell you a lot about what is in that truck. These signs or placards comply with DOT regulations for trucks shipping within the United States and Canada. 

What do all those symbols and numbers mean?

There are four relevant items indicated by these signs as noted by the diagram below.

Class 7 Hazard Placard

Hazard Symbol: An alternate method for identifying the material contained in the tank

Class Name: A one or two word description of the contents of the tank

Color Classification: The color of the placard provides some detail relating to the type of material
 

Red: Flammable Material
Red and White: Flammable Solid or Spontaneously Combustible Material
Orange: Explosives
Yellow: Oxidizer
Green: Nonflammable Material
Blue: Dangerous when Wet
White: Inhalation Hazard and Poisonous
White and Yellow: Radioactive
Black and White: Corrosive
White with Black Stripes: Misc Hazardous Material

Hazard Class: Shipped materials are categorized in one of 9 classes

Class 1: Explosives
Class 2: Gases – Compressed or Refrigerated
Class 3: Flammable and/or Combustible Liquid
Class 4: Flammable Solids – Spontaneously Combustible and/or Water Reactive
Class 5: Oxidizing Materials – Organic Peroxide
Class 6: Poisonous and/or Infectious Substances
Class 7: Radioactive Materials
Class 8: Corrosive Materials
Class 9: Misc. Hazardous Materials

Sometimes in place of the class name, a classification number is used. This is called the United Nations identification number. These numbers are listed on a chart that further classifies the contents of the tank. This number can also be denoted separately from the hazard placard in the form of a rectangular orange label.

Petroleum gases, liquefied

More information and a complete list of these numbers can be found here:

http://en.wikipedia.org/wiki/UN_number

For those of you with a smart phone on hand, there is an app available that provides a database search for the UN numbers. You can get a general description and if you want more information you can click on the listing for more details. The app for Android is called DOT Placards and the app for Apple is called Placard+. 

Should I be concerned if I see a truck hauling radioactive material?

There are many regulations dictating how radioactive material can be shipped. Depending on the radiological strength, these materials fall into 4 different categories:

• Exempt (not strong enough to pose a health hazard)
• Low-level Waste (LLW)
• Intermediate-level Waste (ILW)
• High-level Waste (HLW)

Each of these categories requires a certain type of container and shielding for transport. As summarized by the World Nuclear Association:

“The objective of the regulations is to protect people and the environment from the effects of radiation during the transport of radioactive material.

Protection is achieved by:

• containment of radioactive contents;
• control of external radiation levels;
• prevention of criticality; and
• prevention of damage caused by heat.

The fundamental principle applied to the transport of radioactive material is that the protection comes from the design of the package, regardless of how the material is transported.”

So rest assured that even in the event of an accident, the radioactive material is securely packed to prevent accidental radiation exposure.

References:

World Nuclear Association, “Transport of Radioactive Materials” http://www.world-nuclear.org/Information-Library/
San Bernardino County Fire Dept, Hazardous Materials Division, “Emergency Response Program” http://www.sbcfire.org/hazmat/er.aspx