Using the Atmosphere-Space Interactions Monitor (ASIM) observatory on the International Space Station (ISS), researchers have observed five intense blue flashes, one of which initiated a pulsating blue jet into the stratosphere, over the Pacific Ocean, close to the island of Nauru.
Blue jet: (a) the cloud-top altitude of the storm cell over the South Pacific on February 26, 2019, at 15:10 UTC, derived from the Japanese Himawari meteorological satellite data and from a radio sounding at Tarawa at a distance of approximately 700 km (435 miles); the green curve is the ISS orbit and the red marker its position at 15:10:05 UTC; the black curves identify the full field of view of the cameras projected to the Earth’s surface, and the white square is the cropped image, downloaded from the ISS and shown in (b); black markers are the lightning locations detected by the GLD360 network between 15:10:00 and 15:11:40 UTC; (b) the cropped, downlinked ASIM image (777.4 nm) of the cloud backlit by internal lightning; the source locations of the five blue flash events detected between 15:10:00 and 15:11:35 UTC are shown with colored markers, time progressing from red to yellow. The flash leading to a blue jet is event number 3. Image credit: Neubert et al., doi: 10.1038/s41586-020-03122-6.
“Blue jets are lightning-like, atmospheric electric discharges that fan into cones as they propagate from the top of thunderclouds into the stratosphere of our planet,” said Dr. Torsten Neubert from the National Space Institute at the Technical University of Denmark and colleagues.
“They have durations of several hundred milliseconds and are thought to initiate in an electric breakdown between the positively charged upper region of a cloud and a layer of negative charge at the cloud boundary and in the air above.”
“The breakdown forms a leader that transitions into streamers when propagating upwards. However, the properties of the leader, and the altitude to which it extends above the clouds, are not well known.”
On February 26, 2019, the ASIM observatory detected five intense, approximately 10-microsecond blue flashes from a thunderstorm cell near the island of Naru in the central Pacific Ocean.
One of the observed flashes generated a blue jet into the stratosphere.
The events were accompanied by ‘elves’ — rapidly expanding rings of optical and UV emissions at the bottom of the ionosphere.
“Emissions from lightning leaders in the red spectral band are faint and localized, suggesting that the flashes and the jet are streamer ionization waves, and that the leader elements at their origin are short and localized,” the researchers said.
“We propose that the microsecond flashes are the optical equivalent of negative narrow bipolar events observed in radio waves.”
“These are known to initiate lightning within the cloud and to the ground, and blue lightning into the stratosphere.”
“This study is an impressive highlight of the many new phenomena ASIM is observing above thunderstorms and shows that we still have so much to discover and learn about our Universe,” said Dr. Astrid Orr, of ESA.
“Congratulations to all the scientists and teams that made this happen as well as the engineers that built the observatory and the support teams on ground operating ASIM, a true international collaboration that has led to amazing discoveries.”
The team’s paper was published in the journal Nature.
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T. Neubert et al. 2021. Observation of the onset of a blue jet into the stratosphere. Nature 589, 371-375; doi: 10.1038/s41586-020-03122-6
