Mustafa(pbuh) Prize News

MSTF Media reports:
Lightning is not merely an electrical discharge in storm clouds. Each lightning bolt triggers a series of complex electromagnetic processes that begin in the lower layers of the atmosphere and extend to tens of kilometers above the Earth, even affecting the space environment surrounding the planet. Over the past decades, advances in observational technologies and the expansion of atmospheric physics studies have made it possible to recognize phenomena that were previously only mysterious and unknown lights in the sky, phenomena that are today known as transient optical events.
These events, which include red sprites, elves, and blue jets, appear for only a few milliseconds at altitudes above storm clouds, thus having eluded scientists’ enquiries for years. Understanding the formation of these phenomena has not only helped to better grasp the electrical behavior of the Earth's atmosphere, but has also shed light on the role of lightning in the interaction between the atmosphere and near-Earth space.
We sat with the veteran space scientist, Professor Umran Inan, who is a professor emeritus at Stanford University and a former president of and currently a faculty member at Koc University in Turkey. In 2019, Inan won the Mustafa^(pbuh) Prize for his fundamental research and understanding of whistler-mode wave-particle interaction in near-Earth space, and the electrodynamic coupling between lightning discharges and the upper atmosphere. In our interview with him, Inan talked about his most significant research, his path to discovering transient optical events, the development of observational tools, and the current challenges in understanding these phenomena.

Lightning: A Gateway to the Unknown World of the Atmosphere
For Inan, the study of transient optical events did not begin with the observation of red sprites. He says his research initially focused on studying electromagnetic waves and energetic particles, particles that are trapped in the Earth's radiation belts and whose behavior is affected by different waves.
“There are electromagnetic waves and highly energetic particles, trapped in the Earth's radiation belts that can be used to measure interesting phenomena near the Earth's atmosphere, and these particles undergo interactions that are very similar to the operation of a free-electron laser,” he observed.
According to Inan, further studies revealed that one of the most important factors in creating these waves is the lightning that occurs every day across the Earth. For this reason, his research team’s attention shifted from studying radiation belts to lightning and its role in the space environment around Earth.
Referring to the vastness of this phenomenon, he provides some sobering statistics: “You probably don't know this, but right now, as we speak, between 40 and 60 lightning strikes occur on Earth per second. There are also about two thousand active thunderstorms around the world.” 
The Mustafa^(pbuh) Prize laureate observed that each of these lightning bolts creates very large electrical currents that, like an antenna, send electromagnetic waves into space. The waves interact with energetic particles in the radiation belts and can even affect the intensity of radiation in the space environment around Earth.
This raised an important question for Inan and his colleagues: If there were no lightning on a planet, would the space environment around it be different?
In response to this question, he says, “If there were no lightning, radiation belts would probably be more dangerous for satellites. Since satellites are constantly exposed to high-energy particle radiation, understanding these processes is important.”
Therefore, these observations led his research team to investigate how lightning-generated waves propagate through different layers of the atmosphere; this ultimately led them to the discovery of phenomena that few people knew about until then.

The Lights Seen for Years but Never Identified 
Studying the waves produced by lightning led Inan and his colleagues to observe the upper layers of the atmosphere, where strange, fleeting lights appeared.
Inan says these phenomena occur at altitudes much higher than the location of the lightning strike and even higher than the cruising altitude of commercial aircraft, lasting only between 10 and 20 milliseconds, a time so short that it was almost impossible to record them with conventional equipment.
It was later revealed that the pilots had been observing these lights for years, but due to the unknown nature of the phenomenon and their inability to record it, they rarely talked about these observations.
“When a pilot cannot record what they see, it is natural for them not to talk about it, because others may think they are hallucinating. For this reason, these phenomena were not even reported,” Inan said.
This initiated a new phase of his group's research aimed at capturing images of these mysterious lights and finding an answer to the mechanism of their formation.

Red Sprites Caught on Camera
After Inan and his research team were convinced of the existence of these mysterious lights high in the atmosphere, the more difficult stage began: recording a phenomenon that lasted only a few milliseconds and was not visible with the usual equipment of the time.
Inan’s team then decided to use CCD cameras to record these lights, choosing areas where it was possible to simultaneously observe the lightning and the sky above it. One of these areas was the state of Colorado in the United States.
“When you look out to the horizon from eastern Colorado, there's no visual barrier and you can see the lightning strikes that are happening in the distance over Kansas and other areas,” he maintained. “You see both the lightning and the space above it.”
Such favorable conditions allowed researchers to record lights that appeared dozens of kilometers above storm clouds for the first time.
Inan further added that the lights were seen at an altitude of 10, 20, and even 30 kilometers above the lightning, with a range of about 30 to 60 kilometers. Inan and his students wanted to know why this was happening.

The Secret of the Red Sprites Unveiled
After the first images were captured, the most urgent question was how these lights were formed. Inan says that to answer this question, his team began a thorough study of how clouds become charged and how electric fields behaved during lightning strikes.
According to him, storm clouds gradually become charged due to strong upward air currents. The movement of ice particles and water droplets within the cloud and their collisions with each other cause the separation of electrical charges, ultimately causing a large amount of electrical charge to be stored in the cloud.
“A cloud might carry about 100 coulombs of electrical charge, which is a very large amount,” he explains. “As long as lightning does not occur, the atmosphere gradually adjusts to this charge, but when lightning occurs, a large portion of this charge is suddenly transferred to the ground.”
After this sudden discharge, the upper layers of the atmosphere need time to return to equilibrium, and in the meantime a very large electric field is created.
According to Inan, these electric fields sometimes reach hundreds of kilovolts per meter and accelerate electrons to very high speeds. These electrons collide with nitrogen and oxygen molecules in the atmosphere, and the result of these collisions is the production of light.

Why Are ‘Red Sprites’ Red?
For years, a preoccupation of researchers has been the cause of the red color of this phenomenon.
This is so because, according to Inan, the initial excitation occurs in nitrogen molecules. The electric field accelerates the electrons which then collide with nitrogen molecules, producing red light.
This happens only briefly, usually not lasting more than 20 milliseconds, which is why the human eye only receives a very brief image of it.
To clarify the phenomenon, Inan compared it to video images: “When you watch a movie, each image is just one frame, but the brain sees them continuously. The red sprites only last for a frame or two, which is why they were so difficult to capture.”

‘Elves’: Too Fast for Cameras
In the course of their research, Inan and his team discovered that electromagnetic waves from lightning move towards the ionosphere at very high speeds and, after hitting this layer, spread out in the form of a wide ring.
Known as ‘elves,’ this phenomenon occurs at an altitude of about 90 to 100 kilometers and is so fast that even CCD cameras were unable to record it accurately.
Inan’s team had to design a new tool.

The Fly's Eye: a Tool for Capturing Microsecond Lights
They designed a device consisting of a series of very fast photometers, which was named ‘the Fly's Eye’ because of its structural similarity to insects’ eyes.
“The system consisted of 10 or 12 photometers, each sampling at very high temporal resolution,” he explains. “With the help of the device, we were able to see that the light starts from the center and then spreads out to the sides, exactly as we had predicted.”
Designing this instrument was a crucial step in validating his team's theoretical models, showing that many of their predictions about the formation of transient optical events are consistent with actual observations. However, that wasn't the end of the story.
As the quality of observations increased, newer phenomena also surfaced; from the very fine structures of red sprites to water jets moving from the clouds to higher altitudes, each phenomenon posed new questions for researchers.