Effects of Propagation of Narrow Bipolar Pulses, Generated by Compact Cloud Discharges, over Finitely Conducting Ground

Abstract

Propagation effects on the narrow bipolar pulses (NBPs) or the radiation fields generated by compact cloud discharges as they propagate over finitely conducting ground are presented. The results were obtained using a sample of NBPs recorded with high time resolution from close thunderstorms in Sri Lanka. The results show that the peak amplitude and the temporal features such as the full width at half maximum (FWHM), zero-crossing time, and the time derivative of NBPs can be significantly distorted by propagation effects. For this reason, the study of peak amplitudes and temporal features of NBPs and the remote sensing of current parameters of compact cloud discharges should be conducted using NBPs recorded under conditions where the propagation effects are minimal.

Modeling Compact Intracloud Discharge (CID) as a Streamer Burst

“…They appear to be rather smooth in field records, but high-resolution records show fine structure superimposed on these waveforms [12]. The presence of the fine structure is apparent when one observes the electric field time derivative of these pulses which shows a strong ragged structure which is not present in other high current events such as return strokes [2,14,15]. Figures 1 and 2 show, respectively, examples of NBPs and their time derivatives measured in the study conducted by Karunarathne et al [6] (and summarized by Bandara et al [7]) and Gunasekara et al [11] .…”

On the Accuracy of Ray‐Theory Methods to Determine the Altitudes of Intracloud Electric Discharges and Ionospheric Reflections: Application to Narrow Bipolar Events

“…Other approaches based on full-wave methods such as wave-hop (ray-theory) method, waveguide mode theory, and the finite-difference time-domain (FDTD) method have also been used to determine the ionospheric height as revealed by ground or intracloud lightning discharges in both daytime and nighttime (e.g., Azadifar et al, 2017;Cummer et al, 1998;Han et al, 2011;Han & Cummer, 2010a, 2010bQin et al, 2017;Shao et al, 2013;Tran et al, 2017). The propagation effect of NBE electromagnetic pulses or the radiation fields generated by CIDs over finitely conducting ground is mentioned by Rison et al (2016) and Watson and Marshall (2007), and further investigated by Cooray et al (2018), but their studies were limited to the groundwave part of the NBE signal. The results show that, due to a large amount of high-frequency components for the narrow features of NBEs, the peak amplitude, the zero-crossing time, the full width at half maximum (FWHM), and the time derivatives of the groundwave of the NBEs were significantly distorted by propagation effects over the finitely conducting ground.…”