2023-2024: Atmospheric and Space Electricity: Joseph R. Dwyer

Joseph R. Dwyer 
University of New Hampshire 


Joseph Dwyer received his PhD in physics from the University of Chicago in 1994, working on cosmic-ray astrophysics. He worked as a research scientist at Columbia University and the University of Maryland before joining the faculty at the Florida Institute of Technology in 2000. Dwyer served as head of the Physics Department at Florida Tech before moving to the University of New Hampshire in 2014. He is currently a Professor and Chair of the Department of Physics and Astronomy at UNH as well as the Peter T. Paul Chair in Space Sciences in the Space Science Center, Institute for Earth, Oceans, and Space. 

Over the last 20 years, Joseph Dwyer has played a leading role in establishing and advancing the field of High Energy Atmospheric Physics, making important contributions to our understanding of lightning physics, terrestrial gamma-ray flashes (TGFs) and the x-ray emissions from lightning. His work includes both the theory and observations of energetic radiation and radio frequency emissions from thunderstorms and lightning. He has also made contributions to understanding lightning initiation and propagation, long laboratory sparks in air, cosmic ray physics and space physics. 

Dwyer received the 2014 Karl Berger Award for distinguished achievements in the science and engineering of lightning research from the International Conference on Lightning Protection (ICLP). He became a Fellow of the American Geophysical Union (AGU) in 2019 and was chosen to give the AGU Franklin Lecture that year. His work in public outreach includes articles in Scientific American and appearances in numerous television documentaries and news articles

Abstract: High-Energy Emissions from Thunderstorms and Lightning

Lightning is ubiquitous, striking our planet at least a billion times each year, sometimes hurting people and damaging property. Yet 270 years after Franklin’s famous kite experiment, there are still many basic questions about lightning that remain unanswered, including how it gets started inside thunderstorms, how it travels through air, and how it attaches to objects on the ground. Moreover, during the last few decades, a variety of new and strange high-energy phenomena have been discovered in and around thunderstorms. Terrestrial Gamma-ray Flashes (TGFs), short bursts of gamma rays produced inside thunderstorms, are so powerful they sometimes temporally blind gamma-ray instruments in low-Earth orbit, 600 km above the storms. As the TGF gamma rays travel through the atmosphere, they launch beams of electrons and positrons into the inner magnetosphere, where they are observed as Terrestrial Electron Beams (TEBs) by spacecraft thousands of kilometers away. In addition to TGFs, thunderstorms also produce gamma-ray glows that last from seconds to minutes and are routinely observed by instruments on aircraft and balloons, and from the ground. Some gamma-ray glows contain anomalously strong 511 keV lines, showing that large numbers of positrons are somehow produced by the storms. Finally, lightning leaders emit bright bursts of x-rays as they propagate through clouds and near the ground. Since none of these energetic emissions can be produced by conventional discharges in air, the presence of x-rays and gamma rays shows that other high-energy processes must be occurring. Specifically, it is thought that the energetic radiation is produced by bremsstrahlung emissions from relativistic runaway electrons accelerated in air by strong thundercloud or lightning electric fields. Because this runaway electron production is very sensitive to the electric field, x-ray and gamma-ray observations probe the charge distributions inside thunderstorms and near lightning, thus addressing key questions about lightning initiation, propagation and attachment. In this talk, I will give an overview of the high-energy emissions from thunderstorms and lightning, including how they are observed, how we think they are produced, and what effects they might have on thunderstorm and lightning processes, topics that are all part of the new field of High-Energy Atmospheric Physics.