Jellyfish sprite, a giant lightning that occurs in the mesosphere at an altitude of 50 to 80 km. Observed in Spain. Scientists have discovered that the green glow at the top of this sprite is created by metal particles from space. Green light is not visible to the naked eye./Andalusai Astrophysics Institute, Spain
When thunder strikes, white flashes fall from the clouds to the ground. Lightning falls in streaks as if the sky is split. There was a reason why the weapon used by Zeus, the most powerful god in Greek mythology, was lightning. This is because it is a being that shows at once how scary nature can be.
Zeus’s weapons were not what we saw. Recently, scientists have captured a series of giant lightning strikes occurring above clouds. These monster lightnings are created by particles from space, as if thrown by Zeus, and unlike regular lightning, they can go up into the sky.
◇Ghost lightning in the mesosphere, origins in space
On the 12th, the research team led by Dr. María Passas-Varo of the Astrophysics Institute of Andalusia, Spain, wrote in the international academic journal ‘Nature Communication’, “We know the composition of the mesospheric ghost that appears above the lightning that occurs above the clouds. The mesosphere is a part of the Earth’s atmosphere and refers to the altitude of 50 to 80 km between the stratosphere and the thermosphere.
Spanish scientists have observed red lightning falling 80km above the Mediterranean Sea since May 2019. It is a ‘sprite’, a type of lightning in the upper atmosphere. The lightning pouring down looks like jellyfish tentacles, so it is also called ‘jellyfish sprite’. Immediately after the sprite occurred, a green halo appeared at the top like a ghost and then disappeared. It is a ‘mesospheric ghost’.
The researchers waited for the sprite to fall again at the same location. Finally, on September 21, 2019, a special camera captured the green ghost blinking at the top of the jellyfish sprite lightning. Researchers initially assumed that the green light on lightning was created when oxygen atoms received energy, like polar aurora. As expected, oxygen waves were detected in the ghost. But that wasn’t all.
The researchers revealed that Sprite’s green ghost is created by iron particles from space rather than oxygen. Wavelengths of metals such as iron and nickel along with oxygen and nitrogen came from the green ghost. “There are layers of metal dancing in and around thunderstorms where lightning strikes,” Dr. Passas-Barro said. The researchers explained that iron and nickel came from micrometeoroids falling into the Earth’s atmosphere. Ghosts are guests who have come from space.
Graphics = Son Min-kyun
◇Mega lightning occurring above clouds
Lightning is a phenomenon in which electric current moves in the atmosphere. Air is an insulator that does not conduct electricity. However, if electric charges accumulate in the clouds, they can move through the air where there is no path. Electric charge refers to the amount of electricity an object has. If there are more electrons than protons with a basic charge, it becomes (-), and if there are fewer electrons, it becomes (+).
When electric charges accumulate in the cloud, the voltage increases and current flows for an extremely short period of time, just as a dam fills with water and the water pressure increases. Lightning travels from clouds to the ground. Normal lightning occurs in the troposphere, up to an altitude of 11 km from the ground. However, there are other types of lightning that occur higher than the clouds.
The ghost of the mesosphere analyzed this time is a type of ‘transient luminous event (TLE)’ that was first conceptualized in 1989. Unlike regular lightning, TLE is powerful lightning that occurs above thunderstorm clouds and is also called ‘mega lightning’.
Mega lightning includes sprites that fall up to 15 km from the ionosphere at an altitude of 90 km, and conversely, there are ‘blue jets’ that rise from the top of a thunderstorm cloud to the ionosphere at 70 km above the ground. Above it are the ‘Elves’, which appear horizontally in the shape of a huge donut with a diameter of 400 km in the thermosphere (100 km altitude). The ‘gigantic jet’ is a red sprite above and a blue jet below and rises to an altitude of 90 km.
Giant jet observed in Puerto Rico in September 2019. Above the thunderstorm, the ionosphere rose 70 km in less than a second./Frankie Lucena
◇The reason why lightning strikes upwards is still a mystery
Recently, a series of unusual mega lightning bolts have been captured. On August 20th, photographer Frankie Lucena was photographing a tropical storm in Puerto Rico when he captured several large lightning flashes rising above the storm clouds. It was the Giant Jet.
Giant jets are a rare type of lightning that occurs about 1,000 times a year, and are more than 50 times more powerful than regular lightning. Scientists from the National Oceanic and Atmospheric Administration (NOAA) told Science Advances in August last year that giant jets are also frequently reported when strong storms occur in the Atlantic Ocean.
Giant jet lightning, which is more than 50 times more powerful than regular lightning. It rises to an altitude of 90 km above the thunderstorm clouds. / Frankie Lucena)
Scientists have not yet completely figured out why lightning above clouds goes up rather than down. Last year, NOAA researchers analyzed a giant jet observed in Oklahoma, USA, and found that lightning was likely blocked, unable to escape through the bottom of the cloud. In fact, giant jets are observed in storms where lightning does not often travel from clouds to the ground.
Lightning rising upwards as a blue jet. In 2002, researchers at Pennsylvania State University announced in Nature that they had filmed a blue jet, a type of lightning that rises from the ground to the ionosphere at an altitude of 70 km, using a high-speed camera. Blue jets have been seen from spacecraft and airplanes, but this was the first time they were observed from the ground. The previous record was to reach an altitude of 40 km above the ground.
At the time, researchers estimated that the blue jet moved through a kind of electrical passage between the ground and the ionosphere, given that the voltage difference between the ground and the ionosphere was as high as 300,000 volts.
A blue jet video published in Nature by researchers at Pennsylvania State University in 2002. /Pennsylvania State University, USA
reference material
Nature Communications(2023). DOI: https://doi.org/10.1038/s41467-023-42892-1
Science Advances(2022), DOI: https://doi.org/10.1126/sciadv.abl8731
