When storm clouds send lightning crackling in jagged streaks across the sky or produce a thundering bolt that strikes the ground, another otherworldly phenomenon sometimes erupts from the top of the clouds in a column of blue light firing toward space. These colorful flashes are called blue jets and they can stretch 30 miles into the stratosphere.
Blue jets can only be seen from the ground under rare circumstances because they’re brief and are typically obscured by clouds. But in 2019, instruments aboard the International Space Station (ISS) were able record five blue flashes and a blue jet that shot into space from a storm cloud near the island of Nauru in the middle of the Pacific Ocean.
Now, those observations form the basis of a new paper published in the journal Nature that may help explain what gives rise to blue jets, reports Nicoletta Lanese for Live Science. Per the paper, each of the flashes lasted between 10 and 20 milliseconds and the blue jet reached an altitude of roughly 32 miles above sea level.
According to Live Science, the current, albeit incomplete, understanding of blue jets suggests that they occur when the positively charged upper section of a cloud interacts with a negatively charged layer sitting just above the cloud, briefly equalizing the opposing charges in a bright blue discharge of static electricity. Normal lightning, Maria Temming of Science News explains, occurs when opposing charges in nearby clouds or between a cloud and the ground equalize and discharge their electricity.
The blue jet over Nauru was captured by optical cameras, photometers, and an X-ray and gamma-ray detector mounted on the outside of the ISS. The researchers report that the blue flashes were accompanied by flashes of ultraviolet light called ELVES.
"This paper is an impressive highlight of the many new phenomena ASIM is observing above thunderstorms," says Astrid Orr, physical sciences coordinator for human and robotic spaceflight with the European Space Agency (ESA), in a statement.
Victor Pasko, an astrophysicist at Penn State who was not involved in the work, tells Science News that improving our understanding of blue jets, as well as other unfamiliar but no less real phenomena such as red sprites, is important because they can disrupt the radio waves we use for communication technology. Per Live Science, these upper atmospheric phenomena may also impact the concentrations of greenhouse gases and Earth’s ozone layer.