Physics & Astronomy ETDs

Publication Date

2-8-2011

Abstract

A program has been developed that portrays the fractal modeling of lightning, which subsequently calculates the fields from a fractal antenna. Nodal currents are weighted with branch length. The Hausdorff dimension for various growth parameters η, agree with those in the literature. Electric fields in the far zone have been calculated by weighting the branch currents with an overall damped sinusoidal current. The current waveform for each element is evaluated at retarded times based upon the speed the discharge propagates along the fractal. At scale lengths of 100 m an interference pattern becomes noticeable. We have investigated the slope of the power spectrum for spider lightning. For f < fthreshold the slope is between -1.6 to -2.6 with a standard deviation of ~ 2. In the case of channel lightning this slope would be -2. For f > fthreshold the average slope varies between -3.4 and -3.5. In the case of channel lightning this slope would be -4. The lesser slope is attributed to more interference between radiating elements in this model. For f > fthreshold the slope appears to be independent of the growth parameter. Observations show for inter-cloud lightning the threshold frequency is 50 kHz, with zero slope for f < fthreshold and -1.6 slope for f > fthreshold.

Degree Name

Physics

Level of Degree

Masters

Department Name

Physics & Astronomy

First Committee Member (Chair)

Jeffery, Chris

Second Committee Member

Taylor, Gregory

Project Sponsors

Los Alamos ISR-2 group

Language

English

Keywords

Lightning--Computer simulation, Fractals.

Document Type

Thesis

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