2024-2025: Atmospheric and Space Electricity: Steven Cummer

Steven Cummer 
Duke University 

Biography

Dr. Steven A. Cummer is the William H. Younger Distinguished Professor of Electrical and Computer Engineering at Duke University.  He received B.S., M.S., and Ph.D. degrees in Electrical Engineering from Stanford University, and after 2 years as a postdoctoral fellow at NASA Goddard Space Flight Center, he joined Duke as an Assistant Professor in 2000.  
His geophysics research centers on the development and application of new radio-based remote sensing tools for atmospheric electricity, lightning, and the upper atmosphere. This includes developing radio-based tools to measure lightning currents from long distances and to imaging lightning when it is hidden inside clouds.  With this he has made contributions to understanding how lightning produces high altitude effects such as sprites and gigantic jets, how thunderstorms produce high energy radiation in the form of terrestrial gamma-ray flashes, and how lightning itself initiates and develops.
Dr. Cummer is a Fellow of the American Geophysical Union and the Institute of Electrical and Electronics Engineers.  He is a Clarivate Highly Cited Researcher, and he received a Presidential Early Career Award for Scientists and Engineers (PECASE) in 2001. At Duke his work has been recognized through the Capers and Marion McDonald Award for Excellence in Teaching and Research in 2009 and the Stansell Family Distinguished Research Award in 2018. 


Abstract: Lightning: More Than Meets The Eye

 Over the past 30 years, a wide range of completely unknown phenomena produced by lightning and atmospheric electrical processes have been discovered.  Some of these are visible to the human eye if you are lucky enough to be in the right place at the right time, such as gigantic jets that launch from the tops of thunderstorms to 90 km altitude at the edge of space.  Others are not visible but are just as impressive, such as terrestrial gamma-ray flashes that beam an intense, short burst of high energy photons, electrons, and even antimatter (in the form of positrons) upward into space and sometimes down towards the ground.  And the physics of lightning itself is much more complicated than we knew even just 5 years ago. These discoveries all owe thanks to modern optical and radio imaging techniques that have delivered images and movies with exquisite space and time resolution.  I will describe some the stories of how these phenomena were first documented (almost always through a combination of luck and persistence), and I will show some of the best and most interesting images, videos, and measurements that we have of each.  Adapting to the interests of different audiences, I will also describe their underlying physics (as best we understand them at present) and highlight some key scientific questions that remain unanswered.