| This dissertation presents an examination of natural cloud-to-ground lightning in Florida, experimental data for which were acquired in 2002 to 2004. Several processes involved in natural lightning, in particular stepped leaders and first return strokes, were studied using the electric (E) and magnetic (B) fields and field derivatives (dE/dt and dB/dt) measured at distances ranging from about 50 m to 1 km. The experimental system used, known as the Multiple Station Experiment (MSE) system, consisted of six electric field sensors (bandwidth of 0.2 Hz to 4 MHz), two magnetic field sensors (10 Hz to 4 MHz), four dE/dt sensors (up to 20 MHz), and three dB/dt sensors (up to 20 MHz), spread around an area of about 0.5 km2. The system is located at the International Center for Lightning Research and Testing (ICLRT), and is operated by the University of Florida Lightning Research Group. Between 2002 and 2004, data were acquired for about 20 lightning flashes, including one consisting of both positive and negative strokes, all thought to have terminated on ground within or near the network. The channel locations were estimated by a 2-D time-of-arrival method, using the peaks of the return stroke dE/dt waveforms. The estimated locations were used in performing a statistical characterization of several field waveform parameters (such as the leader and return stroke electric field changes), and parameters of the leader channels (such as the line charge density, speed, and current) were estimated from the acquired waveforms using simple models. Further, new insights into the mechanisms of the stepped leader and ground attachment process were gained from the experimental data and associated modeling. |
