Scientists have observed an unusual event in the clouds triggering a lightning flash. This presented another theory of how air carried electricity inside the storm clouds.

The fast negative breakdown occurred when air moves on an upward path with a velocity one-fifth of the speed of light. This new observation complemented the earlier theory of fast positive breakdown, where air moves on a downward motion, transitioning from a positive charge at the top to negative charge in the middle of the cloud.

Lightning Is A Mystery

Even with 250 years of research, scientists are still puzzled how lightning is initiated. Fast negative breakdown offered a new view on what transpires in a thundercloud during a storm.

"This is the first time fast negative breakdown has ever been observed, so it's very exciting," said co-author Ningyu Liu, who is an associate professor of in the Department of Physics and Space Science Center at the University of New Hampshire.

Lead investigator Julia Tiles said the results of their experiment the creation of lightning in thunderclouds were likely to more bidirectional than originally thought.

"Recent discoveries, such as sprites, jets, terrestrial gamma ray flashes, and fast positive breakdown, highlight the diversity of complex phenomena that thunderstorms can produce, and point to the possibility for electrical breakdown/discharge mechanisms beyond dielectric breakdown theory based mainly on laboratory experiments," said the researchers in a study published in the journal Nature Communications.

Tiles' team, together with scientists from the New Mexico Institute of Mining and Technology, continue to process images from the data. They hope to learn what fraction of fast negative breakdowns can create a lightning flash.

Why Is It Important?

Fast positive breakdowns cause a rare but extremely powerful type of lightning called narrow bipolar events. Its speed is faster than typical lightning at 10 to 100 million meters per second.

Narrow bipolar lightning is the strongest natural source of radiofrequency radiation which can reach for up to a few megawatts. Researchers said this will help them understand how a cloud can generate a magnitude of energy enough to produce lightning.

Electric fields measured inside thunderstorms were far weaker to initiate lightning. Current laboratory capabilities cannot simulate a thunderstorm within a controlled environment.