Ground Conductivity Estimated from Wideband dE/dt Waveshapes of Distant Lightning Sources Near Ground
Abstract
An electric field propagating as a ground wave over finitely conducting ground suffers Ohmic loss, which increases with frequency. This loss is a function of the ground constants (conductivity and dielectric constant) and source height. Ground conductivities were estimated from waveshape differences in dE/dt pulses arising from different propagation distances. The data were wideband dE/dt signals recorded from five measurement sites stations at Kennedy Space Center. A model was used to introduce additional loss into the closer station waveshape so that it matched the more distant station waveshape. up to four conductivities per dE/dt pulse were estimated via pairwise matches with the furthest station waveshape. The waveshapes were matched by using a gradient method to minimize the sum of the squares of the measurement residuals. The geometric mean of 96 ground conductivity estimates was 0.0042 S/m and the geometric standard deviation was 2.0. Both of these values are in line with published values. Errors arising from uncertainties in distance, height, and dielectric constant accounted for only 8% of this standard deviation. However, it was not clear whether the two times spread was caused by system noise or an actual variation in conductivity. System noise was reduced for a handful of pulses by estimating a single conductivity per pulse via the pairwise matching of station data all possible pairs.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 21, 1997
- Accession Number
- ADA341013
Entities
People
- Ewen M. Thomson
- Jim Schueler
Organizations
- University of Florida