Locating lightning from slow-tail measurements recorded at a single station [electronic resource]

This dissertation analyzes the use of single station measurements of low-frequency electromagnetic waves to locate lightning discharges occurring around much of the world. Lightning detection is a useful tool for many commercial and scientific applications, including early forest fire detection, aircraft route planning, climate modeling and atmospheric studies. There exist lightning location methods that use satellite detectors and others that use networks of ground-based receivers. Using only a single ground-based station is a cost efficient method for lightning detection, though it can often be limited in range and accuracy. The electromagnetic waves generated by lightning discharges are known as radio atmospherics, or sferics. Sferics propagate for great distances away from the radiating discharge in the Earth-ionosphere waveguide and can be detected remotely by radio frequency receiving equipment such as those using magnetic loop antennas. To locate the causal lightning stroke from a recorded sferic, the methodology from this thesis combines an existing direction finding algorithm to compute the arrival azimuth along with a distance of propagation estimate. The new method to estimate the distance of propagation relies on modeling the propagation of the slow-tail, the portion of the sferic that falls in the extremely low frequency (ELF: 3-3000 Hz) range. Slow-tail propagation in the Earth-ionosphere waveguide is modeled for a range of propagation distances, and the recorded sferics are compared with the model output to estimate the actual distance of propagation. A solution is introduced for modeling slow-tails that propagate across the day-night terminator. The lightning location estimates from the new method are compared to the lightning recorded by the National Lightning Detection Network (NLDN), which records lightning in North America. Using the newly developed methodology, the direction of propagation estimates from recorded sferics are accurate to within 5° of the NLDN determined direction while the distance of propagation estimates are accurate to within 10% of the NLDN determined propagation distance. Accuracies in this range make this lightning detection method more appropriate for storm detection than individual lightning discharge detection. Some recorded sferics can not be used for this lightning detection method due to interference in the slow-tail signal by a subsequent lightning discharge, leaving approximately 70% of the recorded sferics viable for locating lightning. Attenuation to station location and the station's signal to noise ratio determine the maximum range specific to that station for lightning detection. Lightning location from two different stations are analyzed: Søndrestrøm station (Greenland) and Palmer station (Antarctica). A single station with low noise, such as Palmer, is shown to locate lightning over approximately half the world, increasing the coverage of lightning detection over other existing single station methods.

Keywords: Electrical Engineering
Advisor: Fraser-Smith A. C. (Antony C.) primary advisor. Thesis advisor
Inan Umran S. advisor. Thesis advisor
Walt Martin