Lightning stroke distance estimation from single station observation and validation with WWLLN data

A simple technique to estimate the distance of the lightning strikes d with a single VLF electromagnetic wave receiver at a single station is described. The technique is based on the recording of oscillatory waveforms of the elec- tric fields of sferics. Even though the process of estimat- ing d using the waveform is a rather classical one, a novel and simple procedure for finding d is proposed in this paper. The procedure adopted provides two independent estimates of the distance of the stroke. The accuracy of measurements has been improved by employing high speed (333 ns sam- pling rate) signal processing techniques. GPS time is used as the reference time, which enables us to compare the calcu- lated distances of the lightning strikes, by both methods, with those calculated from the data obtained by the World-Wide Lightning Location Network (WWLLN), which uses a multi- station technique. The estimated distances of the lightning strikes (77), whose times correlated, ranged from 3000- 16 250 km. When d<3500 km, the average deviation in d compared with those calculated with the multi-station light- ning location system is 4.7%, while for all the strokes it was 8.8%. One of the lightnings which was recorded by WWLLN, whose field pattern was recorded and the spectro- gram of the sferic was also recorded at the site, is analyzed in detail. The deviations in d calculated from the field pattern and from the arrival time of the sferic were 3.2% and 1.5%, respectively, compared to d calculated from the WWLLN lo- cation. FFT analysis of the waveform showed that only a narrow band of frequencies is received at the site, which is confirmed by the intensity of the corresponding sferic in the spectrogram.