The weather along the East Coast in the summer can be stifling hot, with humidity levels that you could cut with a blade. In conditions like this, the sudden development of severe thunderstorms is typical.
That’s what occurred in 1984 while on a night fight in a U.S. Navy SH-2F Seasprite helicopter. Our crew spotted bands of intense thunderstorms moving out to sea. As we traveled south along the eastern Florida coastline toward St. Augustine, we saw short bursts of faint but vivid red lightning shooting both upward toward the heavens and downward toward the top of nearly continuous-illuminated convective supercells, lit up like a jack-o’-lantern due to the internal lightning they generated out over the Atlantic.
So what the heck was this red lightning we were witnessing? I thought perhaps it was the reflection of the helicopter’s red anti-conclusion light near the tail rotor that rotated 360 degrees, giving the illusion of red flashes for other aircraft to see. But when we turned it off, we continued to see these fleeting flares of magenta light that danced on top of faraway thunderstorms. At that time, we had no idea what we had observed.
Years later, I discovered that these faint, mysterious bolts of red lightning are called red sprites. There are also blue jets, which I’ve personally never seen. It wasn’t until 1989 that the first photograph of this luminous phenomenon was captured.
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Sprites are faint but vast flashes that only last for a few thousandths of a second and extend into the thermosphere, which starts at about 56 miles above our planet to the edge of the atmosphere. Because they are so high, it’s best to be far away to get a better view. Naturally, nearby clouds and rain can also obscure your observation.
Unfortunately, there’s not a lot of scientific data about sprites. They seem to develop simultaneously with severe thunderstorms below. Lightning is created by turbulence — updrafts and downdrafts — found in thunderstorms that produced friction between rapidly moving ice particles and rain traveling in opposite directions. That wipes off electrical charges, which produce an increase in pressure or voltage. The same effect can sometimes be experienced by rubbing your shoes across a wool carpet on a dry day and then touching a doorknob. The shock you feel is the electricity discharged to the handle.
Most cloud-to-ground lightning is negative, in fact about 95 percent. However, severe lightning storms can produce positive charge lightning strikes to the ground that can disrupt the atmosphere’s electrical field, which can rapidly accelerate charged particles, creating red sprites high in the sky.
Lately, crew members aboard the International Space Station have been capturing images of red sprites at an ever-increasing rate from their sensitive low-light cameras. Weather watchers have also been taking pictures of sprites from the far peripheries of hurricanes by using tripods and long exposures with their digital-single lens reflex cameras. Next time a faraway thunderstorm rolls through at night, glance above its Cumulonimbus clouds and you just might see one.
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I will be speaking at “Sharks After Dark” fundraising event at the Central Coast Aquarium in Avila Beach on climate change and its consequences for California on Thursday, Oct. 19, at 7 p.m. I would love to see you there.
John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at email@example.com or follow him on Twitter: @PGE_John.