Burst of intracloud current pulses during the initial continuous current in a rocket‐triggered lightning flash

Lu, Gaopeng; Jiang, Rubin; Qie, Xiushu; Sun, Zhongchang; Liu, Mingyuan; Wang, Zhichao; Liu, Kun

doi:10.1002/2014gl062127

Cited by 29 publications

(35 citation statements)

References 24 publications

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“…Though no correlation was observed between the pulses of current and VHF radiation, they presumed a stepwise propagation of the positive leader. Referring to the same event, Lu et al () correlated the azimuthal position of the source of magnetic pulses (time correlated with the measured pulses of current at the beginning of the ICC) with that of the tip of the positive leader, as inferred from the VHF radiation field. Note that no conclusions about stepped propagation could have been derived from the observations of VHF radiation, since both continuous and stepped developing leaders are sources of VHF radiation pulses.…”

Section: Discussion On Specific Features Of Upward Leaders In Naturalmentioning

confidence: 99%

Section: The Propagation Mode Of Upward Positive Leadersmentioning

confidence: 99%

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Features of Upward Positive Leaders Initiated From Towers in Natural Cloud‐to‐Ground Lightning Based on Simultaneous High‐Speed Videos, Measured Currents, and Electric Fields

2017

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Original simultaneous records of currents, close electric field, and high‐speed videos of natural negative cloud‐to‐ground lightning striking the tower of Morro do Cachimbo Station are used to reveal typical features of upward positive leaders before the attachment, including their initiation and mode of propagation. According to the results, upward positive leaders initiate some hundreds of microseconds prior to the return stroke, while a continuous uprising current of about 4 A and superimposed pulses of a few tens amperes flow along the tower. Upon leader initiation, the electric field measured 50 m away from the tower at ground level is about 60 kV/m. The corresponding average field roughly estimated 0.5 m above the tower top is higher than 0.55 MV/m. As in laboratory experiments, the common propagation mode of upward positive leaders is developing continuously, without steps, from their initiation. Unlike downward negative leaders, upward positive leaders typically do not branch off, though they can bifurcate under the effect of a downward negative leader's secondary branch approaching their lateral surface. The upward positive leader's estimated average two‐dimensional propagation speed, in the range of 0.06 × 106 to 0.16 × 106 m/s, has the same order of magnitude as that of downward negative leaders. Apparently, the speed tends to increase just before attachment.

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Section: Discussion On Specific Features Of Upward Leaders In Naturalmentioning

confidence: 99%

Section: The Propagation Mode Of Upward Positive Leadersmentioning

confidence: 99%

Features of Upward Positive Leaders Initiated From Towers in Natural Cloud‐to‐Ground Lightning Based on Simultaneous High‐Speed Videos, Measured Currents, and Electric Fields

2017

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“…Continuing current (CC) is defined as the relatively low-level current lasting for tens to hundreds of milliseconds that immediately follows a return stroke (RS) in both natural flashes (Kitagawa et al, 1962;Rakov & Uman, 1990) and triggered flashes (W. Lu et al, 2011;Saba et al, 2016). In order to distinguish from CC, the term initial continuous current is used, which follows an upward positive leader that occurred before a RS in the initial stage in both rocket-triggered (Fisher et al, 1993;G. Lu et al, 2015) and object-initiated lightning (Flache et al, 2008;Miki et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Observation Results and Discussion on an Upward Leader Followed by a Long Continuing Current After a Return Stroke

Shi

Qiu

et al. 2018

Geophysical Research Letters

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An abnormal discharge process after a return stroke (RS) in a negative cloud‐to‐ground flash was studied in detail. Correlating high‐speed video images and electric field data, it was found that the abnormal discharge process was initiated at ground and transported positive charge from ground toward cloud. Moreover, there was a long continuing current (CC) initiated by the abnormal upward discharge process. Compared with the characteristics of RSs, CCs and M components, we conclude that the upward discharge process is a kind of upward positive leader. The 3‐D speeds of the positive leader range from 3.72 × 106 m/s to 14.48 × 106 m/s with average value of 6.5 × 106 m/s. As far as we know, it is the first report that a long CC follows the upward positive leader after RS, which is obviously different from traditional CCs. The discovery is helpful to gain a deeper understanding of the mechanism and physical process of negative cloud‐to‐ground flashes.

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“…Figure shows one example of typical channel‐base current waveform acquired (with a 5 mΩ shunt) for a rocket‐triggered lightning flash (as examined in details by Sun et al [] and Lu et al []) in SHandong Artificially Triggered Lightning Experiment (SHATLE) during the summer campaign in 2013. As shown in the figure, the minimum magnitude of current pulses measured at the channel base is approximately 8 A, and the data are not appropriate for resolving even smaller‐current pulses that have been reported in the literature [e.g., Willett et al ., ; Lalande et al ., , ; Ngin et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Characterization of initial current pulses in negative rocket‐triggered lightning with sensitive magnetic sensor

Zhang

Jiang

et al. 2016

Radio Science

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We report the new measurement of initial current pulses in rocket‐triggered lightning with a broadband magnetic sensor at 78 m distance. The high sensitivity of our sensor makes it possible to detect weak ripple deflections (as low as 0.4 A) that are not readily resolved in the typical measurements of channel‐base current in rocket‐triggered lightning experiments. The discernible magnetic pulses within 1 ms after the inception of a sustained upward positive leader from the triggering wire can be classified into impulsive pulses and ripple pulses according to the discernibility of separation between individual pulses. The time scale (usually >20 µs) of ripple pulses is substantially longer than the leading impulsive pulses (with time scales typically <10 µs), and the amplitude is significantly reduced, whereas there is no considerable difference in the interpulse pulse. Along with our previous finding on the burst of magnetic pulses during the initial continuous current in rocket‐triggered lightning, the new measurements suggest that the stepwise propagation might be a persistent feature for the upward positive leader in rocket‐triggered lightning, and the stepping of positive leader early in triggered lightning could be characterized with the observation of ripple pulses. The precedence of impulsive magnetic pulse measured at 78 m range relative to the arrival of corresponding current pulse at the channel base indicates that the ionization wave launched by individual stepping of positive leader propagates downward along the triggering wire at a mean velocity of 1.23 × 108 m/s to 2.25 × 108 m/s.

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Burst of intracloud current pulses during the initial continuous current in a rocket‐triggered lightning flash

Cited by 29 publications

References 24 publications

Features of Upward Positive Leaders Initiated From Towers in Natural Cloud‐to‐Ground Lightning Based on Simultaneous High‐Speed Videos, Measured Currents, and Electric Fields

Features of Upward Positive Leaders Initiated From Towers in Natural Cloud‐to‐Ground Lightning Based on Simultaneous High‐Speed Videos, Measured Currents, and Electric Fields

Observation Results and Discussion on an Upward Leader Followed by a Long Continuing Current After a Return Stroke

Characterization of initial current pulses in negative rocket‐triggered lightning with sensitive magnetic sensor

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