Designation: President of Koc University, Turkey
Work: Understanding of whistler-mode wave-particle interaction in near-Earth space and the electrodynamic coupling between lighting discharges and the upper atmosphere
Field of the Prize: Ionospheric and Atmospheric Physics
Ümran Savaş İnan; An Intimate Profile
After the midnight of 15 September 2001, Ümran Inan, then a professor of electrical engineering at Stanford University, and his colleagues recorded an astonishing lightning event above thunderstorm cells had clustered 200 kilometers away from their observation site. About a decade earlier, the first case of such events was captured by a camera. So they were waiting for some bizarre kinds of electrical discharges but what they witnessed was beyond their expectation. The event was apparently an upwards lightning, called “blue jet”, but in this case the jet just propagated to the altitude of about 70 km, roughly twice as the upper limit of normal blue jets were observed before.
That night, Inan and his colleagues, In fact, discovered a new type of electrical discharges now known as “gigantic jets”. In their report of the event that published in nature, they noted: “as we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common.” But it turned out that it is not, the gigantic jets are so rare that only about a dozen of them have been observed since then.
Not so Engineer
Ümran Savaş İnan, born in Erzincan, Turkey (1950), emeritus professor of electrical engineering at Stanford University, is internationally recognized as a leading researcher in the study of upper-atmospheric phenomena. Despite his background in electrical engineering for Bachelor’s (1972) and Master’s Degrees (1973) at the Middle East Technical University in Ankara, many of his most cited papers are in the field of near-Earth space physics. When he went to Stanford University for a Ph.D. scholarship, he realized that his research group was working on topics that had much more to do with atmospheric and space physics than engineering. “I was first worried about the fact that this field was too specialized, especially when I return to Turkey,” he says.
In the following, he became interested in the physics and chemistry of the upper atmosphere and while he could switch to any other research group in the electrical engineering department, he stayed in a field that was entirely new and challenging for him. “Because of my deep education from Turkey, my inherent interest in the topic, and because I prefer to be challenged rather than take the easy path, I thus decided to stay,” he says.
However, the decision might have rooted in his childhood. Inan’s father was head of the forecast division of the Turkish Meteorological Service, and obviously Inan, as a kid, might have a tighter bond to atmospheric affairs including lightning than any other kids. His father's job as a public servant also affected his future profession in another way. He was an outdoor-oriented child and used to play soccer and volleyball in their neighborhood along with his two brothers. Every time there was a government change, his father would be worried about being assigned to a new city. Because of those unpleasant movements, Inan didn’t want to work for government, or even in private industry. “At the beginning of high-school, I decided to be an academician. It looked to be the profession in which I could also be my own boss,” he says.
Inan’s decision to be an academician was not just a matter of job preference, he wanted to pursue science, even as a teenager. He was such an eager reader who wouldn’t pass out any text, even those on wrappings or bags made of obsolete newspapers. And, his interest in science grew out of his curiosity and passion for reading. As a regular visitor of the British and the American Libraries in Ankara, when he somehow ran into books about chemistry and physics, he got so obsessed that he decided to set up his own science lab. “I used all my allowance to buy chemistry equipment and actually conduct some dangerous experiment and set up my own laboratory in the balcony of our house,” he recalls.
After receiving Ph.D. degree in Electrical Engineering from Stanford University in 1977, he joined the staff of the faculty as a research affiliate and in 1982 was appointed as an assistant professor in the Department of Electrical Engineering. He became an associate professor in 1985 and receiving the professor title at Stanford University in 1992. During 1997-2010, Inan has served as Director of the Space, Telecommunications and Radioscience (STAR) Laboratory.
Inan has authored or co-authored more than 360 scientific publications. Some of his highly cited papers co-authored by Timothy Bell, his Associate Advisor at Stanford University, who along with Robert Helliwell (1920-2011), his Ph.D. Advisor Professor, were the most influential persons in his scientific career. “I learned so much from both of them. As I became a faculty member and became the Head of our Research Group, it was my turn to mentor both of them and create a fruitful and enjoyable scientific environment for them and our many students,” he says.
After many brilliant years at Stanford University, Inan has begun another professional experience as the President of Koç University in Turkey, since 2009. He says there are some open questions in his field of research that are important on a planetary scale, including “Whether the Earth’s radiation belts would be significantly different if there was no lightning activity in the lower atmosphere?” But he doesn’t have any plans to do further research in this area. However, he doesn’t seem worried about his scientific legacy: “I am pleased to indicate that 15 of the Ph.D. students that I graduated are academics at various universities and they will be pursuing these questions and others, which are still open.”
Inan served as the Principal Ph.D. Dissertation Advisor for 60 students who graduated since 1990. “My career was also greatly influenced by the 60 Ph.D. students whom I supervised,” he says. He considers the successful graduation of these many bright students and friends as “the most important achievement of my career, much more than any papers I have written or scientific talks I have presented.”
He believes the most important of life is integrity in everything that one does and sincerity in dealing with other people. “Genuine friendships and collegiality (friendly cooperation) between people are the most important aspects of life, since at the end of a career, the only things that matter are these friendships and the memories of the good things that you have done with and for people.”
What’s going on up there?
Discovery of lightning between earth and space sent scientists back to the blackboard
A downward progressive flashing crack in the sky and a tremendous sound, a few seconds later. As far as it may concern to most of us this is a perfect definition for lightning, a familiar atmospheric phenomenon that may happen about 50 times per second, or 4 million times a day, across the world. But if you ask the experts, they will tell you that despite centuries of scientific scrutiny and a lot of findings, lightning has remained a strange mystery.
Throughout history, lightning has both fascinated and frightened people by its splendor and might. Ancient Greeks, for example, associated it with Zeus, their most mighty god. However, early scientific experiments on lightening in the mid-18th century, including Benjamin Franklin’s famous experiment with a kite, deciphered the electrical nature of lightning. Even after a modern understanding of lightning developed, the phenomenon continued to amazed lucky observers.
For more than a century, especially after the dawn of aviation, there have been lots of reports describing unusual luminous displays flickering through the upper layers of the sky. Although many of them could be explained by auroras or some kind of strangely illuminated clouds, in certain cases particularly those occasionally observed by pilots during flights above thunderstorms in the night sky, were quite baffling. According to the reports, lightning could happen in strange forms, colors, orientations, and locations.
Seeing is Believing
Until the late 20th century, the scientific community mostly regarded such reports as apocryphal. But in 1990, when John R. Winckler and his colleagues at the University of Minnesota captured one of those enigmatic phantoms using a video camera for the first time, it turned out that there are varieties of lightning of completely new configurations. Winckler’s achievements led to flourishing a whole new activity to record and document these high altitude electrical phenomena. Since then, many strange forms of lightning, from long blue pillar to giant red jellyfish, are discovered.
By the end of the 1990s, it turned out that lightning-like phenomena are not restricted to the low altitude sandwiched between thunderclouds and the ground. In fact, electrical discharges could take place in a wide range of altitudes, from lower atmospheric layers up to 100 kilometers above thunderclouds.
These luminous events, many of which are visible to the naked eye, surprisingly remained undiscovered for so long. Even more surprisingly, way before observing these events, scientists knew some form of lightning could happen high in the atmosphere. They have long known that in higher altitudes where the atmosphere is far less turbulent, ultraviolet rays from the sun cause the gas molecules to lose electrons. This is the process that creates the ionosphere, the electrically conductive envelope around the earth.
Large differences in voltage can exist between storm clouds and the ionosphere, just as they do between clouds and the ground. But what happens in the upper layers is different from what we usually observe as typical lightning strikes to the ground. The density of atmosphere decreases by increasing altitude so the lightning that happens at higher altitudes involves fewer air molecules and creates different shapes and colors.
TLE (Transient Luminous Event) which is the more accurate term for upper-atmospheric lightning falls into four categories: red sprites, elves, blue jets, and gamma-ray events. Despite their fanciful names, scientists have made considerable progress in understanding theses ghostly atmospheric events. One of the pioneering researchers in this field is Umran S. Inan, emeritus professor at Stanford University and the president of Koç University in Turkey, who has a remarkable contribution to theorizing the underlying physics of the TLEs.
Inan, one of the laureates of the 2019 Mustafa Prize from Islamic Countries, and his colleagues at Stanford University were particularly at the forefront of the discovery of red sprites and elves. “The observation of these very common but sub-visual luminous phenomena at altitudes ranging from 50 to 100 km was a surprising discovery in the mid-1990s”, Inan says, but much of the underlying physics and properties of these phenomena were extensively modeled and measured by the works of himself and his many doctoral students.
In 1995, one of the first major theories to explain red sprites and elves was proposed in a paper by Inan, Victor Pasko, his doctoral student at the time, and Timothy Bell, also of Stanford University. They suggested that these events are the consequences of striking a type of lightning to the ground. In the paper, they asserted that following a positively charged lightning strikes to the ground, an electric field is briefly created above the storm. “sudden removal of charge in a lightning discharge leaves a charge imbalance in the medium, which then electromagnetically relaxes and produces luminous glows known as ‘Sprites’ at altitudes 50-70 km, much higher than where lightning occurs”, Inan says.
In the paper that is still one of Inan’s most cited works, they also proposed accelerated atmospheric electrons that are disturbed by striking the lightning to the ground, collide with nitrogen in the upper atmosphere. “Intense impulsive electromagnetic radiation produced by lightning also ionizes Nitrogen molecules as it passes through the ionosphere and produces luminous disks of light known as ‘Elves’ at 100 km altitude”, Inan says.
Pasko says recording giant luminous displays above a distant storm by Winckler in 1989 “was totally serendipitous,” but he believes “it became a threshold for a new field of science.” A field that bridged between heavens and also joint forced scientists of two separated branches of physics. The lower electrically neutral atmosphere is the realm of meteorologists, while space physicists deal with charged particles in the upper atmosphere. The region between these two layers is too high for planes and too short for satellites. “Sprites provide windows toward that region, where before discovering of sprites, was best called the “ignorosphere,” Inan says.
“Our understanding of the Earth’s ionosphere, magnetosphere, and radiation belts is important in the context of a better understanding of our planet and its environment,” Inan says. But in terms of real-world applications, sprites and other sources of fluctuations in the ionosphere may interfere with GPS and satellite signals. Also, some scientists speculate that upper-atmospheric lightning might have other effects including on the ozone layer or global warming. Even NASA concerned they might endanger their precious spacecraft during launching and re-entry.
Regardless of these speculative effects, the definitive effect of such electrical phenomena was reviving the scientific curiosity about lightning, 250 years after Franklin historic experiment. Now, in spite of lots of findings thanks to modern pioneers like Inan, we still don’t exactly know how a thundercloud gets the spark needed to initiate a lightning bolt. In fact, years of measurements have shown the electric field in thunderclouds is about ten times smaller than what lightning needs to initiate. Until deciphering this mystery and the physical mechanisms of other astonishing luminous displays through the ethereal world between earth and space, we have no choice other to admit something like the ancient sense of awe and wonder.