HR: 0800h
AN: AE31B-0173    [Abstracts]
TI: Measurement of D region ionospheric perturbations caused by direct lightning-ionosphere interactions
AU: * Cheng, Z
EM: zc@ee.duke.edu
AF: Duke University, 130 Hudson Hall P.O.BOX 90291, Durham, NC 27708 United States
AU: Cummer, S A
EM: cummer@ee.duke.edu
AF: Duke University, 130 Hudson Hall P.O.BOX 90291, Durham, NC 27708 United States
AB: The first experimental evidence of the impulsive direct coupling of energy released by lightning discharge to the lower ionosphere was reported in the form of early/fast perturbation on sub-ionospherically propagating very low frequency (VLF) signals. Since then, based on modeling and measurements, different mechanisms have been advanced to explain the early/fast sub-ionospheric VLF perturbations such as electrical breakdown associated with sprites and halos or the ionization and heating associated with elves. Using VLF energy from lightning strokes that occurred immediately before and after an intense lightning discharge, we can detect D region disturbances caused by the intense lightning flash. The detailed electron density changes caused by the disturbance are measured by analyzing the broadband VLF propagation changes. We also carefully investigate the causative lighting characteristics such as lightning charge moment and peak current to give additional insight into the perturbation mechanism. Our results suggest that many detectable sub-ionospheric VLF perturbations are created by high peak current lightning strokes probably associated with elves, but some appear to be generated by otherwise unexceptional strokes.
DE: 3324 Lightning
DE: 2435 Ionospheric disturbances
DE: 0933 Remote sensing
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting