Measurement and Modeling of Both Distant and Close Electric Fields of an M‐Component in Rocket‐Triggered Lightning

Abstract

Simultaneous measurements of current and multiple-station electric fields associated with a 5.4-kA-peak M-component in rocket-triggered lightning are presented in this study. A close-range electric field measurement site was located northeast of the triggering site, 195°clockwise from South, at a distance of 78 m, while the distant multiple stations in this study were located southwest of the lightning triggering site (25-48°, clockwise from South) at a distance ranging from 69 to 126 km. Both the fast microsecond-scale and slow millisecond-scale pulses were observed at six distant stations. At the close station, the fast pulse was not noticeable. The magnitude and half-peak width of the fast pulse were in the range of 0.91-1.93 V/m and 2.0-3.0 μs, respectively. The corresponding parameters for the slow pulse were, respectively, in the range of 0.59-1.29 V/m and 20.0-25.1 μs. The time lag between the onset of the channel-base current and the far electric field of the M-component was 18 μs. This time lag was used to deduce the ratio of the M-component channel length and the wave speed. The classical guided wave M-component model proposed by Rakov et al. (1995, https://doi.org/10.1029/95JD01924) to simulate the slow, millisecond-scale field pulse assumes that neither the incident nor the reflected current wave undergoes attenuation even though the wave propagation occurs along a lossy channel. A modified guided wave M-component model is proposed in this study in which the M-component current wave attenuates with an exponential decay. Based on the best agreement achieved between the simulated fields using the modified two-wave M-component model and the observed near and far electric fields, the channel length, the M-component wave speed, and the current attenuation constant were inferred, respectively, as 1.8 km, 1 × 10 8 m/s, and 3 km. It is shown that the modified guided wave M-component model is able to reproduce reasonably well the electric fields both at close and far distance ranges.

An Extension of the Guided Wave M‐Component Model Taking Into Account the Presence of a Tall Strike Object

“…A final remark is in order on the difficulty in distinguishing between the fast pulse resulting from the tall tower and the so-called microsecond-scale pulse associated with the junction process of in-cloud leaders and the grounded, current-carrying channel. Indeed, the fast microsecond-scale pulse which precedes the onset of the slow millisecond-scale pulse is very similar in shape to the sharp peak produced by a tall struck object (e.g., Azadifar et al, 2019;Q. Li et al, 2020).…”

“…Instrumented towers (e.g., Azadifar et al., 2014, 2019; Guimaraes et al.,2014; Ishii et al.,2014; Paul & Heidler, 2019; Pavanello, Rachidi, Janischewskyj, et al., 2007; Pavanello, Rachidi, Rubinstein, et al., 2007; Pichler et al., 2010; Romero et al., 2010; Visacro et al., 2013; Zhou et al., 2011, 2015) have been used to obtain information on lightning currents and the associated electromagnetic fields. Experiments using rocket‐triggered lightning (e.g., Q. Li et al., 2020; Qie et al., 2011; Rakov, 2016, 1995; Thottappillil et al., 1995; Wang et al., 1999; Zhang et al., 2011) also constitute an important source of information to investigate the physics and characteristics of various stages in a lightning discharge, including subsequent return strokes and M‐components.…”

Measurement and analysis of impulse grounding impedance of tower grounding device subjected to artificial lightning M‐component

“…The true type test requires a large‐capacity impulse current generator and a wide test site, which can effectively simulate the actual lightning current discharge process of a single lightning strike. However, studies have shown that the lightning strike process generally includes several return strokes [12] and M‐components [13, 14]. The true‐type test also differs from the actual grounding grid impulse current dissipation characteristics.…”