HR: 08:16h
AN: AE41A-02    [Abstracts]
TI: Observed Electric Fields Associated with Lightning Initiation
AU: * Marshall, T C
EM: marshall@olemiss.edu
AF: Department of Physics and Astronomy, University of Mississippi, University, MS 38677-1848 United States
AU: Stolzenburg, M
EM: mstolzen@phy.olemiss.edu
AF: Department of Physics and Astronomy, University of Mississippi, University, MS 38677-1848 United States
AU: Maggio, C R
EM: crmaggio@phy.olemiss.edu
AF: Department of Physics and Astronomy, University of Mississippi, University, MS 38677-1848 United States
AU: Coleman, L M
EM: leonidas@phy.olemiss.edu
AF: Department of Physics and Astronomy, University of Mississippi, University, MS 38677-1848 United States
AU: Krehbiel, P R
EM: krehbiel@ibis.nmt.edu
AF: Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology,, Socorro, NM 87801 United States
AU: Hamlin, T
EM: thamlin@zeus.nmt.edu
AF: Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology,, Socorro, NM 87801 United States
AU: Thomas, R J
EM: thomas@nmt.edu
AF: Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology,, Socorro, NM 87801 United States
AU: Rison, W
EM: rison@arctic.nmt.edu
AF: Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology,, Socorro, NM 87801 United States
AB: The main goal of this presentation is to determine if conditions exist in a thunderstorm such that a runaway breakdown avalanche could occur. We compare in situ electric field (E) measurements and inferred lightning initiation locations of cloud-to-ground and intracloud flashes to several proposed thresholds for runaway breakdown. For these flashes we estimate the vertical depth and the volume in which E exceeds one or more of the runaway thresholds. The presentation focuses on three cloud-to-ground flashes that initiated in the same thunderstorm region within a few minutes of each other. The maximum measured E in the region was 186 kV m$^{-1}$ at 5.77 km altitude, which for runaway electrons is equivalent to 370 kV m$^{-1}$ at sea level; this E value is 130-183% of the various runaway breakdown thresholds. In addition, the volume where E exceeded the runaway thresholds was estimated to be 1-4 km$^{3}$, with a vertical depth of 1000 - 1200 m. At least within part of this volume (and perhaps in most of it) the vertical scale height for exponential growth of runaway electrons was 100 m or less. Thus for these three flashes the conditions necessary for runaway breakdown existed, and runaway breakdown could have initiated the flashes.
DE: 3324 Lightning
DE: 3304 Atmospheric electricity
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting