Coherency of Lightning Sferics

Abstract

Lightning discharges are natural phenomena that are able to generate energies up to several GJ (Rakov & Uman, 2006). The transient radio waves emitted by the lightning discharges are called "atmospherics", or "sferics" for short. These electromagnetic waves widely cover the frequency spectrum from ∼1 Hz to ∼300 MHz, with relatively large spectral amplitudes in the extremely low frequency (ELF) range and very low frequency (VLF) range and a relative maximum at ∼10 kHz (e.g., Burke & Jones, 1992;Taylor, 1960;Weidman & Krider, 1986). Another source of VLF electromagnetic waves is radio transmitters (Barr et al., 2000).Lightning discharges fall into two major categories: cloud-to-ground discharges (CGs) and in-cloud discharges (ICs), where the CGs exhibit much larger peak currents compared to the ICs (e.g., Betz et al., 2009;Fiser et al., 2010). Cloud-to-ground discharges can lead to serious hazards and are more relevant to human life than ICs. The peak current of CGs has been studied for the purpose of lightning protection (e.g., Chowdhuri et al., 2005;Schulz et al., 2016;Takami & Okabe, 2007;Visacro, 2004), and existing lightning location networks mainly aim at detecting cloud-to-ground discharges with the time-of-arrival (TOA) technique.The ionosphere (σ ≈ 10 −4 Sm −1 − 10 −2 Sm −1 ) and the earth's ground (σ ≈ 10 −3 Sm −1 ) form a natural wave guide with large conductivity boundaries, while the atmosphere in between exhibits a much lower conductivity. This wave-guide is able to guide the propagation of sferics (e.g.

Height Determination of a Blue Discharge Observed by ASIM/MMIA on the International Space Station

“…Most CG strokes (from GLD360) are negative and gathered (vertically lined up on the graph) within sequences which correspond to CG flashes, separated of a few seconds and sometimes a few tens of seconds. The blue discharge at 23:02:41 UTC corresponds to a detection by ENTLN (−18.9 kA) and is not associated with another CG detection within 2 s. According to the wave propagation model introduced by Kolmašová et al (2016) and Kašpar et al (2017), the experimental attenuation coefficient can be calculated by knowing the propagation distances, peak currents, 10.1029/2022JD037460 5 of 20 and measured maximum electric fields of a group of lightning events (Bai & Füllekrug, 2022). In this work, the CG strokes recorded between 23:00:00 UTC and 23:00:05 UTC are used to estimate the experimental attenuation coefficient.…”

“…(2016) and Kašpar et al. (2017), the experimental attenuation coefficient can be calculated by knowing the propagation distances, peak currents, and measured maximum electric fields of a group of lightning events (Bai & Füllekrug, 2022). In this work, the CG strokes recorded between 23:00:00 UTC and 23:00:05 UTC are used to estimate the experimental attenuation coefficient.…”

“…A waveform bank consists of distance‐dependent averaged waveforms, and it is a useful tool to investigate lightning waveform characteristics (e.g., Bai & Füllekrug, 2022; Z. Liu et al., 2018; Said et al., 2010). The waveform bank is used here to calculate the ionospheric height.…”

Height Determination of a Blue Discharge Observed by ASIM/MMIA on the International Space Station

“…5 of 20 and measured maximum electric fields of a group of lightning events (Bai & Füllekrug, 2022). In this work, the CG strokes recorded between 23:00:00 UTC and 23:00:05 UTC are used to estimate the experimental attenuation coefficient.…”

“…A waveform bank consists of distance-dependent averaged waveforms, and it is a useful tool to investigate lightning waveform characteristics (e.g., Bai & Füllekrug, 2022;Said et al, 2010). The waveform bank is used here to calculate the ionospheric height.…”