HR: 11:00h
AN: AE52A-03 INVITED     [Abstracts]
TI: Observations of Sprites Using High Spatial and Temporal Resolution Instruments
AU: * Gerken, E
EM: eag48@cornell.edu
AF: Cornell University, 320 Rhodes Hall School of Elec. and Comp. Eng. Cornell University, Ithaca, NY 14853 United States
AU: Moudry, D
EM: drm@gi.alaska.edu
AF: University of Alaska, Fairbanks, Geophysical Institute University of Alaska Fairbanks , Fairbanks, AK 99775
AB: In the 15 years since the accidental discovery of optical flashes above thunderstorms [{\it Franz et al,} 1990], now commonly termed sprites, the wide variety of spatial and temporal characteristics exhibited by these phenomena has challenged modeling efforts. The highly dynamic and variable structures observed in sprites can be classified either in terms of basic geometric descriptions (``cylinders," ``tendrils," ``branches," etc.) or by their apparent relation to features previously observed in laboratory gas discharges (i.e. ``streamers" and ``diffuse glow"). High-resolution imagery shows that the lower portion of a sprite typically consists of downward branching filaments, or positive streamers, while the middle to upper portions are made up of upward branching filaments, or negative streamers. The topmost part of a sprite is generally amorphous, or diffuse glow. Filamentary structures (streamers) have been observed to range in width from $\sim$20 - 200 m with the radius having some altitude dependence. Much of the observed streamer and diffuse glow structure can be explained in terms of conventional electrical gas discharge physics. Some features such as beads and low-altitude diffuse glows, however, are currently unexplained by any sprite model. This presentation describes the spatio-temporal characteristics of several sprites with various features as observed by 1) a high-spatial-resolution telescope, previously described in {\it Gerken et al.} [2000], with spatial resolution down to tens of meters, and $\sim$17 ms temporal resolution; and 2) similar events observed by a high-temporal-resolution ``high speed imager" with 1 ms temporal and approximately 300 m spatial resolution, previously described in {\it Stenbaek-Nielsen et al.} [2000]. Franz. R. C., R. J. Nemzek, and J. R. Winckler, Television image of a large upward electrical discharge above a thunderstorm, {\it Science, 249,} 48, 1990. Gerken, E. A., U. S. Inan, and C. P. Barrington-Leigh, Telescopic imaging of sprites, {\it Geophys. Res. Lett., 27,} 2637, 2000. Stenbaek-Nielsen, H. C., D. R. Moudry, E. M. Wescott, D. D. Sentman, and F. T. Sao Sabbas, Sprites and possible mesospheric effects, {\it Geophys. Res. Lett., 27,} 3829, 2000.
DE: 3324 Lightning
DE: 3332 Mesospheric dynamics
DE: 3394 Instruments and techniques
DE: 3304 Atmospheric electricity
DE: 0649 Optics
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting