HR: 11:35h
AN: AE52A-05    [Abstracts]
TI: Testing Sprite Initiation Theories Using Lightning Measurements and Modeled EM Fields
AU: * Hu, W
EM: wyhu@ee.duke.edu
AF: Duke University, 130 Hudson Hall, Duke University, Durham, NC 27705 United States
AU: Cummer, S A
EM: cummer@ee.duke.edu
AF: Duke University, 130 Hudson Hall, Duke University, Durham, NC 27705 United States
AU: Lyons, W A
EM: walyons@frii.com
AF: FMA Research, Inc., Yucca Ridge Field Station, 46050 Weld County Road 13, Fort Collins, CO 80524 United States
AB: Previous research has shown that statistical measurements of charge moment changes in sprite-producing lightning are in general agreement with predictions based on conventional breakdown in the mesosphere. Measurements have progressed to the point where a detailed, event-level quantitative comparison between measurements and predictions could more rigorously test existing theories by estimating the electric field above the thunderstorm clouds responsible for sprite initiation. We selected for this analysis a set of sprite events from the summers of 2000 and 2004 whose initiation time is well-bounded from experimental data. Then we measured the current moments and charge moment changes from the recorded electromagnetic fields radiated by the causative lightning strokes. The measured current moments are then used as the input of our 2-D cylindrical full wave finite difference model for simulating lightning-generated EM fields. We compare the simulated mesospheric electric fields to the theoretical threshold electric field for conventional breakdown to see whether, according to theory, a sprite would be initiated by that electric field and at what altitude. By analyzing sprites that are both short and long delayed from the source lightning stroke, we are able compare measurements and theory across a wide range of time scales.
DE: 2411 Electric fields (2712)
DE: 2487 Wave propagation (6934)
DE: 0600 ELECTROMAGNETICS
DE: 0634 Measurement and standards
DE: 0933 Remote sensing
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting