Attention:The NSF Public Access Repository (PAR) system and access will be unavailable from 5:00 PM ET until 8:00 PM ET on Friday, September 11 due to maintenance. We apologize for the inconvenience.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Correlation Between Speed of the Leader and Peak Current of the Return Stroke in Negative Lightning Flashes
Abstract This study analyzes the two‐dimensional speed profiles of 107 stepped leaders and 93 dart leaders recorded by high‐speed cameras in Utah (USA), together with data from lightning location system. The results shows that the final and average speed of the stepped leader has a very strong (R = 0.82) and strong (R = 0.71) correlation with the peak current of the return stroke. It also shows that 91% of the stepped leaders increased their speed near the ground (average increase of 69%). The same analysis for dart leaders shows weak correlation with the peak current of the prospective return stroke (R = 0.39 to average speed andR = 0.28 to final speed). This paper briefly discusses why peak current is better correlated with final speed than with the average speed, and why stepped leaders exhibit a significant correlation, while dart leaders do not.  more » « less
Award ID(s):
2112709
PAR ID:
10598469
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Publisher / Repository:
Geophysical Research Letters, 52, e2024GL111594. https://doi.org/10.1029/2024GL111594
Date Published:
Journal Name:
Geophysical Research Letters
Volume:
52
Issue:
2
ISSN:
0094-8276
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Geophysical Research: Atmospheres)
    Abstract The return stroke in a cloud‐to‐ground (CG) flash is initiated when the downward leader either reaches the ground or connects with an upward leader from a grounded structure. Unlike negative downward leaders, which typically propagate in a highly branched manner, downward positive leaders (DPLs) can propagate either in a branched or unbranched fashion. High‐speed camera recordings show that some DPLs exhibit faint channels accompanied by multiple recoil leaders (RLs)—small bipolar and bidirectional plasma channels—that repeatedly retrace these channels as the leader propagates toward the ground prior to the return stroke (RS). Other leaders, however, consist of a single bright channel with no occurrence of RLs. This study compares the physical characteristics of these two types of DPLs and examines how their propagation modes influence other properties of positive cloud‐to‐ground (+CG) lightning. We show that leaders without RLs propagate significantly faster and are followed by RSs with much higher peak current (Ip) values, on average about twice those associated with leaders accompanied by recoil leaders. The final speed of leaders without RLs exhibits a very strong correlation (R = 0.91) with the RS peak current. The duration of the continuing current (CC) following the RSs is similar for both cases, although there is a slight tendency for longer durations when RLs are present. Analysis of multiple‐stroke +CG lightning flashes with different ground terminations shows that leaders initiating successive strokes can propagate in markedly different ways within time intervals as short as 15 ms. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Geophysical Research: Atmospheres)
    Abstract We report the observation of a downward terrestrial gamma‐ray flash (TGF) during the dart‐leader stage in a negative cloud‐to‐ground lightning flash. The observation was recorded by the Telescope Array Surface Detector, in conjunction with a Lightning Mapping Array, an interferometer (INTF), a fast antenna, and a high‐speed camera. The return stroke was the fifth stroke of a negative cloud‐to‐ground lightning flash, which consisted of nine return strokes (RS) with three distinct ground‐strike points. The peak current of the return stroke associated with the TGF was the highest among the nine RS. Its dart leader had the highest propagation speed in the flash, measuring at m/s. The TGF was detected during the final stages of the dart leader, lasting 68 s. The TGF emission was detected within a few microseconds of the return stroke, indicating that it persisted until the final stage of leader development. The total deposited energy of 1,352 MeV was recorded by the TASD; the fluence was estimated to be 8 at the source, and the source altitude was estimated at 1.45 km above the ground. The observation of a downward TGF associated with a dart‐leader stage supports the idea that the production of X‐rays and downward TGFs are part of a continuum of energetic radiation related to lightning leaders. 
    more » « less
  3. ; ; ; (, Scientific Reports)
    Abstract Information on the temperature of lightning sub-processes is crucial to constrain the chemical and energetic impacts of lightning. However, the peer-reviewed literature on even the most energetic of these processes is scant. In this article, we present a method for measuring these temperatures using the Spectrally-resolved OPtical Automated Photometric Instrument at Langmuir LAb (SOPAPILLA), a near-infrared photometer array that enables a larger number of temperature measurements than previously possible. Across 23 lightning return strokes in the field of view of the instrument, the average peak temperature was 34.8 kK which was weakly correlated with the peak current as reported by a lightning location network. Additionally, in 33 subsequent return strokes reusing the same channel, the temperature of the precursor dart leader (15 kK) was only 3.5 kK cooler (on average) than the ensuing return stroke. We also recorded a close-range powerful stepped leader that displays stepwise temperature enhancements. Finally, by measuring the temperature of M-components (23.5 kK on average) we determine that a return stroke followed by continuing current managed to sustain a temperature of 20 kK for at least 10 ms, cooling slowly at a rate of 1.5 kK/ms. 
    more » « less
  4. ; ; (, Meteorology and Atmospheric Physics)
    null (Ed.)
    Abstract Time-correlated high-speed video and electric field change data for 139 natural, negative cloud-to-ground (CG)-lightning flashes reveal 615 return strokes (RSs) and 29 upward-illumination (UI)-type strokes. Among 121 multi-stroke flashes, 56% visibly connected to more than one ground location for either a RS or UI-type stroke. The number of separate ground-stroke connection locations per CG flash averaged 1.74, with maximum 6. This study examines the 88 subsequent strokes that involved a subsequent stepped leader (SSL), either reaching ground or intercepting a former leader to ground, in 61 flashes. Two basic modes by which these SSLs begin are described and are termed dart - then - stepped leaders herein. One inception mode occurs when a dart leader deflects from the prior main channel and begins propagating as a stepped leader to ground. In these ‘divert’ mode cases, the relevant interstroke time from the prior RS in the channel to the SSL inception from that path is long, ranging from 105 to 204 ms in four visible cases. The alternative mode of SSL inception occurs when a dart leader reaches the end of a prior unsuccessful branch—of an earlier competing dart leader, stepped leader, or initial leader—then begins advancing as a stepped leader toward ground. In this more common ‘branch’ mode (85% of visible cases), there may be no portion of the subsequent RS channel that is shared with a prior RS channel. These two inception modes, and variations among them, can occur in different subsequent strokes of the same flash. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Journal of Geophysical Research: Atmospheres)
    Abstract High‐speed video records of a single‐stroke positive cloud‐to‐ground (+CG) flash were used to examine the evolution of eight needles developing more or less radially from the +CG channel. All these eight needles occurred during the later return‐stroke stage and the following continuing current stage. Six needles, after their initial extension from the lateral surface of the parent channel core, elongated via bidirectional recoil events, which are responsible for flickering, and two of them evolved into negative stepped leaders. For the latter two, the mean extension speed decreased from 5.3 × 106to 3.4 × 105and then to 1.3 × 105 m/s during the initial, recoil‐event, and stepping stages, respectively. The initial needle extension ranged from 70 to 320 m (N = 8), extension via recoil events from 50 to 210 m (N = 6), and extension via stepping from 810 to 1,870 m (N = 2). Compared with needles developing from leader channels, the different behavior of needle flickering, the longer length, the faster extension speed, and the higher flickering rate observed in this work may be attributed to a considerably higher current (rate of charge supply) during the return‐stroke and early continuing‐current stages of +CG flashes. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email