By Frank Ross
As creatures bound to the earth, we are typically more concerned about what comes from the bottom of violent storm clouds and protecting ourselves, our loved ones and our property from those threats. Being focused on the business end of a storm, most people have given little thought to what might be happening above the top of these towering dispensers of rain, lightning, tornadoes and hail. We spend the moments before a storm hits, running for shelter and hoping it is not us that gets lit up by the next blinding bolt, and not our property that gets wiped out by the electrical surge crackling through our electronics.
Although lightning puts on a dazzling display, lashing out from the bottoms of clouds to objects below, sometimes the most impressive show is taking place out of the tops of the thunderheads. And, in these rare cases, the most interesting aspect of this lofty lighting display is the presence of sprites, elves and blue jets.
This image gives a graphic illustration to three extremely illusive electrical events.
Although mankind may have been aware of this atmospheric curiosity for many years or even thousands of years, scientists began their attempt to study, evaluate and document “reported” sightings back in the late 1800s. The earliest known entries in scientific journals date back to 1886, when notations were made of unexplained observations above thunderstorms. A little over 100 years later, on July 6, 1989 the “official discovery” was made by a University of Minnesota Physics Professor, John R. Winckler. Winckler was testing a low-light video camera for a pending rocket flight to conduct research. While playing back the tape, he and his graduate students, Robert Franz and Robert Nemzek, were amazed when they observed giant columns of light towering high above the distant thunderstorms they had taped in northern Minnesota. Immediately they realized their tape had captured evidence of unexplained visual reports of strange lights above thunderstorms dating back over a century.
Once documented, these several electrical events needed names, and numerous options sprang up from the scientific community. However, the one that stuck was sprite. In mythology and Shakespearean plays, “sprites” are mythical, fleeting, and playful creatures, and the observable experience of this particular event fits the name well. As new transient luminous events (TLEs) above thunderstorms were discovered, they were given names in much the same manner. For example, blue jets just named themselves because they looked just like… well, blue jets.
Shortly after Professor Winckler’s discovery, NASA officials realized that they had been using similar low-light cameras on the Space Shuttle. When they conducted a review of the payload bay video cameras used in missions from 1989 to 1991, they discovered at least 18 examples of what appear to be sprites. Then in 2003, Ilan Ramon, the first Israeli astronaut, flew on the STS-107 mission with optical equipment designed to make detailed, calibrated images of sprites. Within several days of launch, successful images of sprites and elves were sent back to earth for further analysis.
Sprites are very brief and difficult to see. The portion of the event that is visible to the naked eye typically lasts less than one hundredth of a second. They’re primarily red in color, although they may have a bluish tinge in the downward extending tendrils. When using a night vision camera, they are visible for longer periods of time, but even with this ultra sensitive technology, they are rarely visible more than one tenth of a second. To complicate the task of documenting and studying sprites even more, sprites often start at altitudes of 45 miles, or in the middle atmosphere. Sprites can appear as low as 15 to 20 miles up, but they tend to extend upwards to the edge of the ionosphere, which is around 55 to 60 miles above the surface of earth.
The limiting factors are color and height, but the upside is size. Sprites are huge, stretching upward for as much as 45 miles with a width that can extend up to 10 miles. Often sprite events can involve a series of individual sprites that occur in clusters which stretch 50 miles or more across the sky. In terms of volume, the amount of atmosphere involved can cover thousands of cubic miles.
Beyond the fact that this atmospheric phenomenon occurs in the lofty confines of our upper atmosphere, it is also fairly rare, produced by a small percentage of less than 10% of cloud-to-ground lightning, and even then only in certain storms. Sprites are composed of many networks of thin channels of electrical streamers, created by the discharge of extremely powerful lightning, sometimes occurring within thunderstorms. Most often they are triggered by a powerful positive cloud-to-ground flash which lowers massive amounts of electric discharge to the earth. This momentarily increases the electric field in the middle atmosphere, which is beyond the point of dielectric breakdown. In plain English, a giant spark starts around 45 miles above the earth, followed by electrical streamers that race both downwards and upwards from the point of origination.
A critical detail to note is that sprites do NOT shoot up from the cloud. They actually start many miles above the storm which creates them, extending both upwards and downwards.
As far as personal observation, the majority of sprites are probably just a bit too dim and too fast to be seen easily by the naked eye. But given the right conditions, one can visually observe sprites on the brighter end of their scale. To date, sprites have been observed over the majority of the world’s surface, with the exception of the Arctic and Antarctic regions where thunderstorms are almost non-existent. The High Plains of the United States is one of the most prolific regions in the U.S. These high rates of occurrence are due to frequent and large nocturnal thunderstorms during spring and summer. Although this region of the U.S. is particularly productive, sprites are likely to be common above storms in northwestern Mexico, Argentina and southern Brazil as well as central Africa. In addition to these regions, sprites have been photographed over Europe, Japan, Peru, China and Australia, just to name a few.
Elves
The elve is another high altitude electrical phenomena, first theoretically predicted by Stanford University scientists back in the early 1990s. Following their prediction, elves were later confirmed by actual observations and photographed from the Space Shuttle and the ground (by Tohoku University scientists) several years thereafter.
Elves are created by an especially powerful electromagnetic radiation pulse (EMP) emanating from certain lightning discharges. Energy passing upwards through the base of the ionosphere causes gases to blow briefly. Although elves are as bright as sprites, elves are far more brief and difficult to document. Typically, elves only last less than a thousandth of a second making them virtually impossible to see with the naked eye. They tend toward the red end of the spectrum, and when seen, look like giant expanding doughnuts. They occur at a height of around 60-65 miles, expanding outward to several hundred miles in diameter.
Blue Jets
Blue jets are similar in origin, but distinctly different. Like the illusive sprite, the first blue jet was “captured,” quite by accident. The University of Alaska-Fairbanks were using low-light cameras onboard a NASA research jet in 1994, which provided the first taped evidence of jets that appear to spurt upwards from cloud tops at speeds of 50-100 miles per second. Jets can reach heights of up to 25 miles before fading from sight. Jets last generally less than a quarter of a second, but it is possible to perceive their upward motion with the naked eye. Typically jets are generated by storms with high lightning rates, but unlike red sprites, blue jets do not appear to be related to specific cloud-to-ground lightning discharges. It also appears that Blue jets are more likely to occur near the highest portion of intense thunderstorm cells, such as those which produce tornadoes and extremely severe weather.
To view any of these three electrical events, it is best to be within 100 or so miles of an active storm. Your best opportunity would be on a moonless night in a rural area away from city lights. Under these conditions the eye adapts quickly to the dark, which helps in spotting these quick, elusive light shows.
If you’re going to try and spot one of these remarkable lightning-related events, just remember that you’re still subject to the effects of lightning coming from the lower region of these storms, so don’t let them get too close before you seek shelter; and hopefully you’ll be seeking that shelter in a home or business with a good lightning protection system installed.
If not, log on to stormgrounding.com for information on the latest in high-quality copper components used in lightning protection systems. The elves, sprites and blue jets will take care of themselves!
