Lightning location using the slow tails of sferics

Abstract

[1] Electromagnetic waves produced by lightning strikes, known as sferics, and their extremely low frequency components, known as slow tails, propagate across the Earthionosphere waveguide. The properties of the recorded time domain slow tail vary with the causative lightning strike's current moment, the waveguide's characteristics, and the distance of propagation. These variations allow us to approximate the location of a causal lightning strike by examining the corresponding sferic. Many methods require measurements from multiple stations; however, the goal of this work is to approximate the distance a sferic propagated using measurements from a single station. J. R. Wait developed an analytical model that describes the propagation of the slow tail along a uniform path in the Earth-ionosphere waveguide. We examine different source functions and apply them to Wait's propagation model in order to ascertain a new and more accurate method for modeling slow tails while improving the accuracy of locating lightning using a single station. Further, we expand the model to include sferics propagating in a nonuniform ionosphere, i.e., crossing the day-night terminator. This new method provides improved correlation of computed slow tails to recorded ones, leading to a more accurate distance approximation for a larger set of sferics.

Single‐Station Lightning Location Using Azimuth and Time of Arrival of Sferics

“…We have introduced a novel method to estimate the propagation distance and the emission time of sferics using recorded data from a single station. Our method is more accurate and more widely applicable than the Ogawa method while being less resource intensive than other single‐station methods (Mackay & Fraser‐Smith, ) as well as multistation methods, like the NLDN.…”

“…However, Wait's method suffers from limited accuracy. An average error of 45.1% for daytime conditions with a standard deviation of is reported for his method (Mackay & Fraser‐Smith, ). Wait assumed a certain analytical form for the lightning current moment, which nonideally can be used to model the ELF component of the sferic.…”

World coverage for single station lightning detection

“…This requires a strong signal in the specified frequency range, limiting the distance of propagation of the sferic when applying this method. In the work of Mackay and Fraser‐Smith [2010], we deduced the distance of propagation by analyzing the slow tail of the sferic. This method can be used for sferics propagating over a wide variety of distances.…”

“…Remote stations record the electromagnetic waves emitted by the lightning which forms a signal known as a sferic. In the work of Mackay and Fraser‐Smith [2010] the ELF portion of the sferic, or the slow tail, is used to compute the distance between the causal lightning and the recording station using the propagation model described by Wait [1960a]. With a direction finding algorithm and this computed distance, the lightning location can be deduced from a single station.…”

New application of wavelets in magnetotelluric data processing: reducing impedance bias

“…4b, c, the highest coefficients obtained with the Morlet wavelet span a wide time length, i.e., longer than the actual length of the ELF wave. Because of their impulsive nature, sferics have a wide frequency content (Mackay and Fraser-Smith 2010). In the time-frequency domain, sferics appear as a series of high-valued coefficients along the frequency axis (very localized in time and spread out in frequency).…”