Conveners:
Mark Stanley (stanleym@lanl.gov), Los Alamos National Laboratory
Victor Pasko (vpasko@psu.edu), The Pennsylvania State University
Mike Taylor (mtaylor@cc.usu.edu), Utah State University
Workshop Format: short presentations
2005 July 01, 0800-1000 AM, Eldorado Sunset Room
This workshop will focus on recent experimental and theoretical advances in the understanding of terrestrial gamma-ray flashes (TGFs), sprites, and other unusual atmospheric discharge phenomena which influence the stratosphere, mesosphere, and beyond.
Sprites are spectacular luminous glows which occupy volumes in excess of thousands of cubic kilometers in clear air above thunderstorms in the altitude range ~40-90 km. Sprites often exhibit an amorphous non structured glow at their tops, which gradually converts to highly (predominantly vertically) structured breakdown regions at lower altitudes. Sprites are transient in nature and last only a small fraction of a second following intense positive or negative lightning discharges (more than 90% of sprites are associated with positive lightning discharges). Observations from ground and from space indicate that sprites occur over most regions of the globe (in temperate and tropical areas, over the oceans, and over the land).
Terrestrial gamma-ray flashes (TGFs) have been observed by the RHESSI satellite with photon energies exceeding 20 MeV. Recent evidence indicates a strong relationship between TGFs and a certain type of lightning discharge. The gamma rays are almost certainly the result of bremsstrahlung from a high energy electron beam. Unlike sprites, TGFs are focused mainly in the tropics and readily occur during daylight. It has been widely assumed that TGFs occur at high altitude (overlapping with sprites) in order to produce an observable gamma-ray flux in orbit, though recent data is challenging this assumption.
This year's workshop will discuss plans for the summer 2005 campaigns in the USA and elsewhere as well as coordinated observations with RHESSI (TGFs) and FORMOSAT 2 (sprites). New modeling and theoretical studies will also be presented.
Schedule:
0800-0900 AM Four invited talks: 12min each w/ 3min for discussions