Joint radio and optical observations of the most radio-powerful intracloud lightning discharges

Jacobson, A. R.; Light, T. E.; Hamlin, T.; Nemzek, Robert J.

doi:10.5194/angeo-31-563-2013

Cited by 23 publications

(32 citation statements)

References 52 publications

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“…Even a small number (<≃10) of repeated individual streamers over such distances is predicted to intensify the field at their starting origin by an order of magnitude 15 32 , explaining how even initially weak breakdown could intensify and lead directly to a more complete discharge. That high-power NBEs are produced by a system of optically dim streamers also explains the deficiency of their optical radiation 36 .…”

Section: Discussionmentioning

confidence: 95%

Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

et al. 2016

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A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.

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Section: Discussionmentioning

confidence: 95%

Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

et al. 2016

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“…Jacobson et al () jointed radio and optical observations of the NBEs (or CIDs) from Fast On‐Orbit Recording of Transient Events (FORTE) satellite and from the ground. The coordinated observations from FORTE satellite included the VHF receiver (frequency range 26–48 MHz) and the photodiode detector (passband 0.4–1.1 μm).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, we conjecture that most of the ISUAL type II GJs may be initiated by a ÀNBE occurring at a high altitude between the upper positive charge layer and the negative screen charge layer atop even though only one associated sferic of the type II GJ is found and related to a ÀNBE discharge. Jacobson et al (2013) 1.1 μm). The ground-based sferic-optical observation included the Los Alamos Sferic Array (frequency range from 160 Hz to 500 kHz; Shao et al, 2006) and the all-sky silicon photodiode (response 350-1,100 nm).…”

Section: 1002/2017ja024793mentioning

confidence: 97%

ISUAL‐Observed Blue Luminous Events: The Associated Sferics

Chou

Hsu

et al. 2018

JGR Space Physics

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The blue luminous events (BLEs) recorded by ISUAL (Imager of Sprites and Upper Atmospheric Lightning) radiate unambiguous middle ultraviolet to blue emissions (230–450 nm) but contain dim red emissions (623–754 nm). The BLE appears to be dot‐like on one ISUAL image with an integration time of 29 ms. A few BLEs develop upward into blue jets/starters or type II gigantic jets (GJs). The associated sferics of the BLEs in the extremely low frequency to very low frequency band and in the low‐frequency band exhibit similar patterns to the narrow bipolar events (NBEs) identified in the very low frequency and low‐frequency band. The ISUAL BLEs are conjectured to be the accompanied light emissions of the NBEs. Both upward and downward propagating current obtained from the associated sferics of the BLEs have been found. The source heights of the six BLEs related to negative NBEs are estimated in the range of 16.2–17.8 km. These six events are suggested to occur between the upper positive charge layer and the negative screen charge layer on the top of the normally electrified thunderstorm. The six blue starters, one blue jet, and one type II GJ are inferred to be positive upward discharges from their associated sferics in the extremely low frequency to very low frequency band. Based on the simultaneous radio and optical observations, a NBE is conjectured to be the initiation discharge with rapidly flowing current within the thunderstorm, while a blue jet/starter or a type II GJ is suggested to be the ensuing discharge with slowly varying current propagating upward from the thunderstorm.

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“…Some publications refer to the source of a NBE as a “compact intracloud lightning discharge” [e.g., Nag et al , ; Rakov , ]. In the present work we use the terminology “narrow bipolar event” [e.g., Eack , ; Jacobson et al , ] (equivalent to narrow bipolar pulse [e.g., Smith et al , ; Thomas et al , ]), because it describes the electric field change waveform, as shown in Figure a. This choice is motivated by the analogy with the name “initial breakdown pulse,” which also refers to the electric field change phenomenology (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Physical mechanism of initial breakdown pulses and narrow bipolar events in lightning discharges

Silva

Pasko

2015

JGR Atmospheres

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To date the true nature of initial breakdown pulses (IBPs) and narrow bipolar events (NBEs) in lightning discharges remains a mystery. Recent experimental evidence has correlated IBPs to the initial development of lightning leaders inside the thundercloud. NBE wideband waveforms resemble classic IBPs in both amplitude and duration. Most NBEs are quite peculiar in the sense that very frequently they occur in isolation from other lightning processes. The remaining fraction, 16% of positive polarity NBEs, according to Wu et al. (2014), happens as the first event in an otherwise regular intracloud lightning discharge. These authors point out that the initiator type of NBEs has no difference with other NBEs that did not start lightning, except for the fact that they occur deeper inside the thunderstorm (i.e., at lower altitudes). In this paper, we propose a new physical mechanism to explain the source of both IBPs and NBEs. We propose that IBPs and NBEs are the electromagnetic transients associated with the sudden (i.e., stepwise) elongation of the initial negative leader extremity in the thunderstorm electric field. To demonstrate our hypothesis a novel computational/numerical model of the bidirectional lightning leader tree is developed, consisting of a generalization of electrostatic and transmission line approximations found in the literature. Finally, we show how the IBP and NBE waveform characteristics directly reflect the properties of the bidirectional lightning leader (such as step length, for example) and amplitude of the thunderstorm electric field.

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Joint radio and optical observations of the most radio-powerful intracloud lightning discharges

Cited by 23 publications

References 52 publications

Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

ISUAL‐Observed Blue Luminous Events: The Associated Sferics

Physical mechanism of initial breakdown pulses and narrow bipolar events in lightning discharges

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