They reveal the origin of “ghosts,” a type of temporary light event in the atmosphere

In the Mesospherea region of the atmosphere that was believed in lack of electrical activityGigantic and short flashes of light are created, the discovery of which surprised the scientific community just three decades ago. Given his elusive characterreceived name taken from Midsummer Night’s Dream (from William Shakespeare), as “elves” or “elves”.

These rare events, related to thunderstorm lightning but located dozens of kilometers above the clouds, include “Ghosts‘ (or GHOSTs, from English Green optical emission from sprite tops), greenish glow, the origin of which was traced back to oxygen.

The “ghosts” are observed in the upper area of ​​the “sprites” (goblins), a spectacular light event lasting hundreds of seconds, showing a diffuse upper part and a lower area with tentacles

Now the first thing spectroscopic examination of these events, published in the magazine Nature communicationcombines them with metals, such as iron or nickelwhich was never included in optical models of mesospheric flares.

The “ghosts” do not appear isolated, but are observed in the upper area of ​​the “sprites” (goblins), a spectacular light event lasting only hundredths of a second, showing a diffuse upper part and a lower area populated by what appear to be tentacles (ionized air threads between 10 and 100 meters thick).

The “goblins” can spread from 40 to almost 100 kilometers above the ground and sometimes represent a type of “goblin”.greenish spirit on the diffuse upper part, which lasts hundreds of milliseconds after the disappearance of the “goblin” that created it.

A ghost (greenish lightning) on ​​a goblin. /Thomas Ashcraft.

“Since the first ‘Transient Light Events’ (or TLEs) were documented in 1989, which is why we know this family of events, people around the world have tried to capture them during the event Thunderstorm. And actually it was Amateur scientist who photographed a ghost for the first time, the last member of the TLE family to be discovered,” he points out Maria Passas VaroResearcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who leads the work.

Until now, the main hypothesis to explain this greenish flash that occurs in some more intense “goblins” was based on the interaction of charged particles (ions) with the atomic oxygen present in it the atmospherea phenomenon that has already been identified in the greenish color of the northern lights. To confirm this, the scientific team that developed this work launched a systematic observation campaign in June 2019 to obtain these data Specters of the upper region of the “Goblins” (A spectrum allows us to know parameters like temperature or composition of a celestial object).

“One in 100 very intense goblins creates a ghost. We analyzed more than 2,000 spectra and only 42 corresponded to the upper “goblin” region, where “ghosts” usually appear. It takes a lot of luck and a lot of skill to aim the instrument at the right height because of the slot in it surveillance It’s very tight and you have to predict where the elf will appear. Of the 42 spectra, only one had a sufficiently intense signal-to-noise ratio,” explains Passas Varo.

This spectrum revealed for the first time what creates “ghosts,” a process that involves very little oxygen. Instead, the team found that the greenish glow was primarily due to metals, iron and nickel, compounds that had never been considered in the study develop optical models for TLEs.

A red goblin (indicated by the white arrow) above a storm, captured by members of the Expedition 44 crew aboard the International Space Station on August 10, 2015. / NASA.

“Just that day we observed some gravitational waves atmospheric disturbances generated by intense vertical movements in the air, such as those generated by Storms“, says the author.

“We knew there were these in the atmosphere layers of metals, that come from the entrance interstellar dustand everything indicates that these variations in air density make the height of these layers variable: this variability would therefore be responsible for the ‘ghosts’“, Explain.

The discovery of these metal atoms implies an update of the models for transient light events, the understanding of which, in turn, is fundamental to understanding the functioning of the global electrical circuit on the planet.

REFERENCE

M. Passas et al. “Spectroscopy of a Mesospheric Ghost Reveals Iron Emissions”. Nature communication (2023)

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