HR: 0800h
AN: AE31B-0171    [Abstracts]
TI: Balloon Observations of the Electromagnetic Fields from Quasi-Planar Ionizing Solitary Waves Associated With Sprites
AU: * Bering, E A
EM: ebering@mail.uh.edu
AF: University of Houston Department of Physics, 617 Science and Research I, Houston, TX 77204 United States
AU: Benbrook, J R
AF: University of Houston Department of Physics, 617 Science and Research I, Houston, TX 77204 United States
AU: Sentman, D D
EM: dsentman@gi.alaska.edu
AF: University of Alaska Geophysical Institute, University of Alaska, Fairbanks, AK 99775 United States
AU: Stenbaek-Nielsen, H C
EM: hnielsen@gi.alaska.edu
AF: University of Alaska Geophysical Institute, University of Alaska, Fairbanks, AK 99775 United States
AB: The University of Houston conducted 3 balloon flights to study sprite electrodynamics during the Sprites99 balloon campaign. During this campaign, the University of Alaska performed a series of optical sprite observations from the Wyoming Infrared Observatory (WIRO) on Jelm Mountain. One of the cameras was a white light 1000 frame/sec high-speed imager (HSI) that permitted following sprite dynamics at millisecond time scales and spatial resolutions of a few hundred meters. The best balloon flight occurred on the night 21 August 1999. A number of sprites exhibiting a variety of complex forms over a wide range of brightness were recorded the night of 18 August 1999 over two thunderstorms centered over Kansas and the South Dakota-Minnesota border, $\sim$700 km from WIRO. Twelve separate events were observed simultaneously by the balloon and by the HSI. An analysis of contrast enhanced images of sprites from this storm revealed several more examples of the previously unreported type of weak ($\sim$several hundred kR), diffuse emission associated with most events that were discussed in the previous talk. In time lapse sequences the diffuse emissions give the visual appearance of downward expanding puffs of smoke launched from the bottom ends of tendrils at $\sim$60 km altitude, reaching diameters $\sim$ 5-10 km over $\sim$5-10 ms, for an average apparent expansion speed of $\sim$1000 km/sec. Several of the events clearly exhibited an effect analogous to limb brightening, suggesting the emissions originated in expanding shells of $\sim$1-2 km thickness. Other events, unaccompanied by immediate streamers, were observed to originate near 75 km and propagate downward as quasi-planar sheets of weak optical emissions. The previous talk suggested that some of the puzzling features of ELF/VLF electromagnetic emissions associated with sprites may derive from charge transport by ionizing solitary waves. This paper will present a detailed examination of the electric and magnetic field perturbations observed by the balloon during these sprites and compare them with the HSI data.
UR: http://www.uh.edu/research/spg/Sprites99.html
DE: 3324 Lightning
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 3304 Atmospheric electricity
DE: 0342 Middle atmosphere--energy deposition
DE: 0654 Plasmas
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting