Physics and Astronomy Colloquium - Caitano da Silva, Penn State University
Title: "Lightning Physics, Related High-Energy Processes, and Their Interactions with the Upper Atmosphere"
Abstract: For thousands of years lightning has been one of the most astonishing natural phenomena, being both frightening and fascinating. Lightning is known to play an important role in the atmospheric system: thunderstorms and lightning are the current source for the global electric circuit, lightning is the main non-antropogenic source of nitrogen oxide in the troposphere, and it is believed that lightning contributed to the formation of organic molecules necessary for the formation of life in the early stages of the planet. Concurrently, lightning discharges are known to be a major source of damages for a wide range of objects and systems, including: miniature electronic integrated circuits, overhead and underground electric power and communication systems, buildings, boats, aircrafts, launch vehicles in flight, and forests (i.e., as a source of forest fires). The modern science of lightning and atmospheric electricity is characterized by the emergence of two research areas, as described below.
The second one investigates high-energy processes associated to lightning and thunderstorms. This research area ignited when a low-orbit satellite aimed to detect gamma-rays from cosmic origin, accidentally identified sources coming from the Earth’s atmosphere below. Twenty years after its discovery, the true physical mechanism of terrestrial gamma ray flashes is still under investigation. Meanwhile, many other aspects of high-energy atmospheric electricity have been determined, such as minute-long gamma-ray glows from thunderstorms and x-rays generated by stepping lightning leaders. The high-energy footprints of lightning and thunderstorms carry very important information on how lightning is initiated inside thunderstorms and on the mechanisms of lightning channel propagation. Their possible deleterious effects on airplanes and crew still have to be quantified. This presentation will provide an overview on recent progress in lightning physics, related high-energy processes, and their interactions with the upper atmosphere.