Correlated Sub-microsecond E-field and High-Speed Image of the Natural Lightning Attachment Process

Wang, D.; Chen, Mingli; Takagi, Nobuyuki; Watanabe, Teiji

doi:10.4271/2001-01-2882

Cited by 4 publications

(18 citation statements)

References 9 publications

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“…The upward leader was initiated when the downward leader, having an average speed of 4 × 10 6 m s −1 , was about 300 m above ground. Wang et al [2001] could not provide an explanation for the unipolar electric field pulse; but the low altitude of the correlated optical signal and the timing and shape of the electric field pulse, consistent with the data presented here, suggest that the pulse resulted from a LB. If we continue this line of reasoning, the work of Wang et al [2001] shows that the LB produces an observable light emission and occurs after the initiation of the upward positive leader.…”

Section: Discussionsupporting

confidence: 42%

“…It may be significant that these pulses coincided with the LB. No previous pulses could be attributed to an upward leader, which is expected to have a duration of tens to a couple hundred microseconds [e.g., Yokoyama et al , 1990; Wang et al , 2001], and the sustained current of the slow front began immediately after the second current pulse. We note that upward positive leaders were imaged with this stroke, as the video frame in Figure 15 shows.…”

Section: Data and Analysismentioning

confidence: 99%

“…Generally, low‐luminosity upward connecting leaders and the rapid processes of the attachment phase are unresolved using these techniques; however, some of these studies, along with still photography [e.g., Golde , 1967; Orville , 1968; Hagenguth , 1947], have provided indirect evidence of upward connecting leaders. More recent studies, such as those using the Automatic Lightning Discharge Progressing Feature Observation System (ALPS) optical imaging system [ Yokoyama et al , 1990; Wang et al , 1999, 2001], have imaged and estimated speeds for upward connecting leaders. Additionally, Biagi et al [2009] presented high‐speed video images that unambiguously identified an upward connecting leader for eight consecutive strokes in a rocket‐triggered lightning flash, although no speed could be estimated for them.…”

Section: Introductionmentioning

confidence: 99%

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RF and X‐ray source locations during the lightning attachment process

et al. 2010

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[1] Using an eight-station array of electric field derivative (dE/dt) sensors and colocated NaI X-ray detectors, we have obtained 3-D RF source locations during the leaders and attachment processes of three first strokes initiated by stepped leaders in natural cloud-toground lightning and one stroke initiated by a dart-stepped leader in a rocket-and-wire triggered flash. Stepped leader and dart-stepped leader dE/dt pulses are tracked from a few hundred meters to a few tens of meters above ground, after which pulses of different characteristics than the step pulses are observed to occur at lower altitudes. These postleader pulses include: (1) the ''leader burst,'' a group of pulses in the dE/dt waveform occurring just prior to the slow front in the corresponding return-stroke electric field waveform; (2) dE/dt pulses occurring during the slow front; and (3) the fast-transition or dominant dE/dt pulse that is usually associated with the rapid transition to peak in the return-stroke electric field waveform. Additionally, the timing coincidence between X rays and dE/dt pulses on colocated measurements is used to examine the X-ray production by the postleader processes. Leader bursts (LBs) are the largest X-ray producers of the three postleader processes and exhibit propagation speeds that exceed the preceding stepped leader speeds by more than an order of magnitude. Slow-front (SF) and fast-transition pulses appear to originate from similar physical processes, probably the multiple connections of upward and downward leaders. However, more X-rays are coincident with slow-front pulses than with fast-transition pulses.

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Section: Discussionsupporting

confidence: 42%

Section: Data and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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RF and X‐ray source locations during the lightning attachment process

et al. 2010

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“…While the timing of the optical pulse relative to the slow front reported by Wang et al . [] might suggest the pulse was associated with the leader burst process, the altitude of the pulse (35 m) relative to the tip of the UCPL (88 m) is contradictory to the observations of this study which place the leader burst pulses within the immediately vicinity of the connection region between the upward and downward leaders.…”

Section: Discussionmentioning

confidence: 99%

“…Wang et al . [] documented a low‐altitude (about 35 m above ground) pulse of light measured with the ALPS photodiode imaging system that occurred less than 2 µs prior to the onset of the slow front in a negative cloud‐to‐ground discharge that terminated about 2 km from the measuring station. The electric field pulse radiated by the optically observed feature was also recorded and had risetime of about 500 ns.…”

Section: Introductionmentioning

confidence: 88%

The attachment process of rocket‐triggered lightning dart‐stepped leaders

et al. 2016

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Time‐correlated 1.54 µs high‐speed video frames, channel‐base current and current derivative (dI/dt), and electric field derivative (dE/dt) measurements are used to analyze the attachment process of triggered lightning dart‐stepped leaders. Lengths, speeds, and durations of the upward‐connecting positive leaders propagating from the launching structure are measured and calculated. The “leader burst” occurring immediately preceding the dE/dt slow front is demonstrated to be a distinctly different process from the preceding downward dart‐stepped leader steps and is associated with the fast increase in channel‐base current due to the initial interactions of the downward and upward leader streamer zones. Locations of the leader burst pulses are found to occur within or immediately above the connection region. Pulses superimposed on the dE/dt slow front are shown to occur after the initial connection between the downward and upward leaders and are associated with kiloampere‐scale increases in the channel‐base current. Subsequent fast‐transition pulses are found to produce multiple kiloampere‐scale increases in the channel‐base current. Observed time delays between dE/dt and dI/dt peaks for slow front and fast‐transition pulses confirm the existence of an elevated junction point between the downward and upward leaders. Average downward current wave speeds for fast‐transition pulses are found to be a factor of 2 to 2.5 faster than those for slow‐front pulses. For 51 dart‐stepped leader events, the average total duration of the attachment process, starting with the initial fast current increase and ending with the peak of the final dI/dt fast‐transition pulse, is measured to be 1.77 µs.

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Lightning attachment processes of an “anomalous” triggered lightning discharge

et al. 2014

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Using a high-speed optical imaging system specifically designed for observing the lightning attachment process, we have documented the process for stepped, dart, and dart-stepped leaders in an anomalous rocket-triggered lightning flash that terminated on a 10 m grounded utility pole. The initiation of the first return stroke was found to occur at a height of 23 ± 3 m above the top of the utility pole and was associated with three "slow front" dE/dt pulses. A time of 1.5 μs later, a fast rise in luminosity at 18 ± 2 m was associated with a "fast transition" dE/dt pulse. The first return stroke propagated bidirectionally from its initiation height, as did subsequent return strokes from their initiation heights of 8 ± 1 m to 16 ± 2 m above the top of the utility pole. The initial upward speed of the first return stroke was 1.4 × 10 8 m/s, while its initial downward speed was 2.2 × 10 7 m/s. The channel bottom luminosity of the first return stroke rose more slowly to a two or more times larger amplitude than that of the subsequent stroke luminosities. In contrast, the National Lightning Detection Network-derived first-return-stroke peak current is smaller than that of the second and the third strokes, and our electric field records at 45 km show similar behavior for the initial field peaks of the first and subsequent strokes.

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Correlated Sub-microsecond E-field and High-Speed Image of the Natural Lightning Attachment Process

Cited by 4 publications

References 9 publications

RF and X‐ray source locations during the lightning attachment process

RF and X‐ray source locations during the lightning attachment process

The attachment process of rocket‐triggered lightning dart‐stepped leaders

Lightning attachment processes of an “anomalous” triggered lightning discharge

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