Conveners: Matt Heavner, MJ Taylor
Tuesday, June 15, 1999 3:30 - 5:30 PM
The purpose of the Transient Optical Emissions in the Upper Atmosphere workshop is to provide the sprites, jets, and elves community an informal forum to discuss recent observations, analysis, and modeling efforts. The overarching theme of the workshop is morphology. Three main types of events are easily distinguished: sprites, primarily red optical emissions (with blue tendrils at lower altitudes) occurring above thunderstorms between 40-95 km, with duration on the order of 10 ms; jets, blue phenomena propagating upward from thunderstorm tops at speeds of 100 km/s to terminal altitudes of 50 km with a duration of 200-300 ms; and elves, brief (1 ms or less) red emissions occurring at the upper altitudes of sprites, associated with the electromagnetic pulse of a cloud-to-ground (CG) lightning discharge. One type of sprite, columniform or "c-sprite", has been identified based on video observers (Wescott, et al. 1998). Using ELF/VLF observations, Reising et al, 1999 have found two distinct types of sprites based on the delay between the sferic from the causative CG lightning and a signature associated with the sprite. Observations of phenomena lasting ~17 ms yet only reaching altitudes of ~50 km have recently been reported by Taylor et al, 1999.
Initial efforts at morphological description of sprites have been based on characteristics observed by imagers (Desroschers et al, FAGU 1995, Moudry et al, FAGU 1998). The goal of the workshop is to widen the scope of the morphological characterization of sprites, using several measurements to aid in the classification scheme. The successful development of a classification scheme by a majority of the sprites research community will lead to a published summary which will be of use to all investigators. Attention will be given to understanding how the developed morphology correlates with the total energetics of the sprites.
The workshop will begin with a brief (~10 minute) introduction to the past decade of transient optical emission research, followed by the presentation of an initial effort towards a categorical classification of sprites. All attendees are invited to present examples of "challenges to classification", suggestions for the classification scheme, or a brief discussion of a sprite observed by multiple instruments and how the observations contribute to the classification scheme. Time permitting, current (summer 1999) observational efforts (dates of observations, instrumentation) will be discussed at the end of the workshop with the aim of increasing collaboration.
Please contact Matt Heavner (heavner@gi.alaska.edu) via email if you are interested in scheduling presentations or have any input to the workshop. The workshop will provide two TV/VCR units (in order that videotapes may be queued up at the same time video data is being presented), a viewgraph projector, and laptop projection facilities.