Gigantic Jet
We're all well acquainted with lightning. The bright, brief flashes of electrical energy puncture the general monotony of Earth's sky. Their luminous dance, however, is restricted to within and below the planet's billowing thunderclouds. Often shielded from our view above is a light show of a more magnificent nature. Here can be seen transient bursts of luminous plasma, the most common of which is a sprite, resembling a red mushroom cloud between 50 and 100 kilometers above the surface. Lucky onlookers can also see blue jets, bold, yet wispy blue bolts extending upwards from the tops of clouds to as high as 40 to 50 kilometers.

Rarest of all the "lightning above the clouds" is the gigantic jet, which is like a supersized blue jet that transitions to the color red at the highest altitudes. Scientists at the Arecibo Observatory once observed a blue jet extending from a thundercloud up to 70 kilometers, blazing at speeds of roughly 2,000,000 meters per second, more than forty times faster than ground lightning!

What sparks these bright behemoths? This was the topic of a recent study published to Scientific Reports. Researchers from the Florida Institute of Technology and the University of New Hampshire made use of different radar variables, lightning data, and lightning simulations to theorize what exactly goes on within a thundercloud.

Gigantic Jet
© Gemini Observatory/AURA/Frankie Lucena
A gigantic jet seen from the Gemini Observatory on Mauna Kea in Hawaii.
The charge structure of thunderclouds is typically similar to an Oreo, with a negatively-charged creme filling sandwiched between two scrumptious cookies representing layers of positive charge. Rarely, a path of negatively-charged ionized air called a leader can escape from the upper positive layer and release streamers than make it all the way to the ionosphere. When this happens, you get a gigantic jet.

According to the new research, brief 'convective pulses' corresponding to a sudden and rapid storm intensification are required for a gigantic jet to occur. In rare cases, this turbulent situation can roil the tidy charge layers enough for a negative leader to escape the upper positive layer and travel to the skies above.

In 2013, NASA installed a device called 'Firestation' specifically designed to study gigantic jets and other forms of lightning above the clouds. When research from this experiment rolls in, we could see these brilliant phenomena in entirely new light!

Source: Levi D. Boggs, Ningyu Liu, Jeremy A. Riousset, Feng Shi, Steven Lazarus, Michael Splitt & Hamid K. Rassoul. "Thunderstorm charge structures producing gigantic jets." Scientific Reports volume 8, Article number: 18085 (2018)