Joseph R. Dwyer (born 1963) is an American physicist known for his lightning research. He is a Professor of Physics at the University of New Hampshire. Dwyer received his Ph.D. in Physics from the University of Chicago in 1994 and worked on cosmic-ray physics and gamma-ray astronomy as a research scientist at Columbia University and the University of Maryland before joining the faculty at the Florida Institute of Technology in 2000. After moving to Melbourne, Florida, Dwyer became interested in lightning physics and his research now focuses on high-energy radiation production from thunderstorms and lightning. In 2002, Dwyer and collaborators discovered that rocket-triggered lightning produced large quantities of x-rays, allowing for first the time detailed studies of an atmospheric phenomenon known as runaway breakdown. In 2014, Dwyer left the Florida Institute of Technology and joined the University of New Hampshire.
In 2002 Dwyer, along with colleagues from Florida Institute of Technology and the University of Florida, launched rockets during thunderstorms at a facility now known as the UF/Florida Tech International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. Using a heavily shielded instrument containing a scintillation detector, built by Dwyer and his students, they found that lightning does indeed produce x-rays and that x-ray emission is common for lightning. This research was published in Science (journal) (Dwyer et al. 2003). Since that time, Dwyer and his collaborators have established many key properties of the x-ray emissions from lightning, including the fact that the x-ray emission is produced during the lightning stepping process, has energies up to approximately 1 MeV and the x-rays are produced in the high field regions generated by the leader as it propagates. In 2005 TERA (Thunderstorm Energetic Radiation Array), a 24 detector array, was built to continue measuring x-rays and gamma-rays from lightning and to further study the x-ray characteristics that are associated with thunderstorms. Also, in 2005, Dwyer and collaborators made the surprising discovery that long laboratory sparks in air also generate x-rays similar to lightning, which has since motivated many groups around the world to study the x-ray emissions from sparks. Most recently, Dwyer and his team have built and deployed an x-ray camera at the ICLRT and have made the world’s first x-ray images of lightning. Dwyer also has made several important theoretical contributions to the newly developing field of High Energy Atmospheric Physics, including work on runaway electron or runaway breakdown physics, gamma-ray and radio frequency emissions or atmospheric noise, and lightning initiation. In 2003, he introduced the Relativistic Feedback Mechanism of relativistic-runaway-electron avalanches, a new discharge mechanism in air, which explains how thunderclouds may generate very large flashes of gamma-rays called terrestrial gamma-ray flashes (TGFs). This work also showed the importance of positrons (anti-electrons) for thundercloud electrodynamics. Working with David Smith from UCSC he also helped establish that TGFs originate from deep within our atmosphere and not at high altitudes as had been previously assumed. Indeed, Dwyer and his team observed a ground level TGF at Camp Blanding in 2004. Finally, using BATSE data form the Compton Gamma-ray Observatory, Dwyer and collaborators discovered Terrestrial Electron Beams (TEBs)  in the inner magnetosphere, which are generated by the high energy emissions from thunderstorms.
Dwyer has written and/or co-authored over 100 scientific research papers, more than 40 of them on lightning, terrestrial gamma-ray flashes, and x-rays from lightning. He has provided content to the PBS/NOVA website on lightning. He has spoken at many university colloquia, conferences, and workshops on his work. His work has also appeared on multiple documentaries, including Nova ScienceNow, Discovery Channel, the weather channel and BBC. Dwyer is the director of the Geospace Physics Lab at Florida Institute of Technology, advisor of graduate students, a member of the American Geophysical Union, and helps Florida Institute of Technology jointly operate the International Center for Lightning Research and Testing with the University of Florida lightning research group.
- List of American scientists
- List of physicists
- List of people from Florida
- List of University of Chicago alumni
- "Energetic Radiation Produced During Rocket Triggered-Lightning". Science. 4 January 2004. Retrieved 4 January 2005.
- "X-ray bursts associated with leader steps in cloud-to-ground lightning". Geophysical Research Letters. 31 January 2003. Retrieved 31 January 2003.
- "Measurements of x-ray emission from rocket-triggered lightning". Geophysical Research Letters. 13 March 2004. Retrieved 13 March 2004.
- "Implications of x-ray emission from lightning". Geophysical Research Letters. 18 June 2004. Retrieved 18 June 2004.
- "Properties of the x-ray emission from rocket-triggered lightning as measured by the Thunderstorm Energetic Radiation Array (TERA)". Journal of Geophysical Research. 15 September 2009. Retrieved 15 September 2009.
- "X-ray bursts produced by laboratory sparks in air". Geophysical Research Letters. 22 October 2005. Retrieved 22 October 2005.
- "High‐speed X‐ray images of triggered lightning dart leaders". Journal of Geophysical Research. 26 October 2011. Retrieved 26 October 2011.
- "A fundamental limit on electric fields in air". Geophysical Research Letters. 25 October 2003. Retrieved 25 October 2003.
- "Remote measurements of thundercloud electrostatic fields". Journal of Geophysical Research. 7 May 2009. Retrieved 7 May 2009.
- "Source mechanisms of terrestrial gamma-ray flashes". Journal of Geophysical Research. 20 May 2008. Retrieved 20 May 2008.
- "Chance of thunder—and gamma-ray flashes". Physics. 3 January 2011. Retrieved 3 January 2011.
- "A ground level gamma-ray burst observed in association with rocket-triggered lightning". Geophysical Research Letters. 13 March 2004. Retrieved 13 March 2004.
- "High-energy electron beams launched into space by thunderstorms". Geophysical Research Letters. 31 January 2008. Retrieved 31 January 2008.
- "Lightning: Expert Q&A". NOVA. 1 October 2005. Retrieved 1 October 2005.
- "How Lightning Works". NOVA. 1 October 2005. Retrieved 1 October 2005.
- "Cosmic Rays Could Reveal Why Lightning Strikes". Discovery News. 9 June 2009. Retrieved 9 June 2009.
- "Antimatter caught streaming from thunderstorms on Earth". BBC News. 11 January 2011. Retrieved 11 January 2011.