Sponsor
This research was partially supported by DARPA grants HR0011‐08‐1‐0088 and HR0011‐1‐10‐1‐0061, NSF grant ATM 0852869, and NASA grant NNK10MB02P.
Published In
Journal of Geophysical Research
Document Type
Article
Publication Date
8-2011
Subjects
Space charge -- Density, Electric fields -- Mathematical models, Lightning
Abstract
We infer the vertical profiles of space charge density and electric field intensity above ground by comparing modeling and measurements of the ground-level electric field changes caused by elevating grounded lightning-triggering wires. The ground-level electric fields at distances of 60 m and 350 m were measured during six wire launches that resulted in triggered lightning. The wires were launched when ground-level electric fields ranged from 3.2 to 7.6 kV m−1 and the triggering heights ranged from 123 to 304 m. From wire launch time to lightning initiation time, the ground-level electric field reduction at 60 m ranged from 2.2 to 3.4 kV m−1, with little ground-level electric field reduction being observed at 350 m. We observed that the triggering heights were inversely proportional to the ground-level electric field when the wires were launched. Our Poisson equation solver simulates the ground-level electric field changes as the grounded wires extend in assumed vertically varying profiles of space charge density and electric field intensity. Our model reproduces the measured ground-level electric field changes when the assumed space charge density decays exponentially with altitude, with ground-level charge densities between 1.5 and 7 nC m−3, space charge exponential decay height constants ranging from 67 to 200 m, and uniform electric field intensities far above the space charge layer ranging from 20 to 60 kV m−1. Our model predicts typical charge densities on the wires of some tens of μC m−1 with milliampere-range currents flowing into the wires from ground to supply the wire charge.
DOI
10.1029/2011JD015710
Persistent Identifier
http://archives.pdx.edu/ds/psu/10611
Citation Details
Biagi, C. J., M. A. Uman, J. Gopalakrishnan, J. D. Hill, V. A. Rakov, T. Ngin, and D. M. Jordan (2011), Determination of the electric field intensity and space charge density versus height prior to triggered lightning, J. Geophys. Res., 116, D15201.
Description
This is the publisher's final PDF. Originally published in Journal of Geophysical Research (http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2169-8996) and is copyrighted by American Geophysical Union (http://www.agu.org/)