Title: Sprites, Halos and Elves in the Upper Atmosphere: What are They,a nd Where do They Come From?


Abstract: Since their discovery in 1989, sprites have become just one member of the ever-growing family of Transient Luminous Events (TLE) in the upper atmosphere. We now distinguish between sprites, jets, halos, and elves. They are all related to large thunderstorms because their prime physical origin is the electrical discharge in lightning. Over the past decade most has been learned from ground- or airplane-based optical or low frequency observations. It was only in May of this year that the first specifically designed optical instrument was launched for a systematic global observation of these phenomena. The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) is a collaborative project between the Taiwanese space agency NSPO, National Chung-Keng University (Taiwan), Tohoku University (Japan) and the Space Sciences Laboratory of UC Berkeley. With a designed lifetime of 5 years it will perform the first global survey of the occurrence frequency and local and seasonal distribution of TLE. The presentation will be divided into two parts. First, the physics of TLE and their optical properties will be discussed. Second, the technical details of ISUAL will be described and first results of the mission will be demonstrated.