 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.