An experimental study of negative discharge in a 1.3 m point-plane air gap: the function of the space stem in the propagation mechanism

Reess, Thierry; Ortéga, Pascal; Gibert, A.; Domens, P.; Pignolet, P.

doi:10.1088/0022-3727/28/11/011

Cited by 54 publications

(76 citation statements)

References 5 publications

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“…The negative space leader extremity becomes the new leader head and the process is repeated [Bazelyan and Raizer, 1998, p. 255]. The formation of a space leader ahead of the negative leader is a fundamental stage in the leader progression, as evidenced in laboratory [e.g., Ortega et al, 1994;Reess et al, 1995;Bazelyan and Raizer, 1998;Gallimberti et al, 2002] and lightning [e.g., Biagi et al, 2009Biagi et al, , 2010Hill et al, 2011] observations. Although positive and negative leaders exhibit different dynamical features, it can be seen, from the above discussion, that the streamer-to-leader transition (or in other words, the air heating) is a fundamental process that defines leader propagation in both cases.…”

Section: Phenomenology Of Positive and Negative Leadersmentioning

confidence: 99%

Dynamics of streamer‐to‐leader transition at reduced air densities and its implications for propagation of lightning leaders and gigantic jets

2013

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[1] In this paper we present modeling studies of air heating by electrical discharges in a wide range of pressures. The developed model is capable of quantifying the different contributions for heating of air at the particle level and rigorously accounts for the vibration-dissociation-vibration coupling. The model is validated by calculating the breakdown times of short air gaps and comparing to available experimental data. Detailed discussion on the role of electron detachment in the development of the thermal-ionizational instability that triggers the spark development in short air gaps is presented. The dynamics of fast heating by quenching of excited electronic states is discussed and the scaling of its main channels with ambient air density is quantified. The developed model is employed to study the streamer-to-leader transition process and to obtain its scaling with ambient air density. Streamer-to-leader transition is the name given to a sequence of events occurring in a thin plasma channel through which a relatively strong current is forced through, culminating in heating of ambient gas and increase of the electrical conductivity of the channel. This process occurs during the inception of leaders (from sharp metallic structures, from hydrometeors inside the thundercloud, or in virgin air) and during their propagation (at the leader head or during the growth of a space leader). The development of a thermal-ionizational instability that culminates in the leader formation and propagation is characterized by a change in air ionization mechanism from electron impact to associative ionization and by contraction of the plasma channel. The introduced methodology for estimation of leader speeds shows that the propagation of a leader is limited by the air heating of every newly formed leader section. It is demonstrated that the streamer-to-leader transition time has an inverse-squared dependence on the ambient air density at near-ground pressures, in agreement with similarity laws for Joule heating in a streamer channel. Model results indicate that a deviation from this similarity scaling occurs at very low air densities, where the rate of electronic power deposition is balanced by the channel expansion, and air heating from quenching of excited electronic states is very inefficient. These findings place a limit on the maximum altitude at which a hot and highly conducting lightning leader channel can be formed in the Earth's atmosphere, result which is important for understating of the gigantic jet (GJ) discharges between thundercloud tops and the lower ionosphere. Simulations of leader speeds at GJ altitudes demonstrate that initial speeds of GJs are consistent with the leader propagation mechanism. The simulation of a GJ, escaping upward from a thundercloud top, shows that the lengthening of the leader streamer zone, in a medium of exponentially decreasing air density, determines the existence of an altitude at which the streamer zones of GJs become so long that they dynamically extend (jump) all the way to th...

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Section: Phenomenology Of Positive and Negative Leadersmentioning

confidence: 99%

Dynamics of streamer‐to‐leader transition at reduced air densities and its implications for propagation of lightning leaders and gigantic jets

2013

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“…Such studies have been performed earlier by several groups. Here we refer in particular to the early work in France [21,22]. Les Renardieres group investigated static, streak and Schlieren photos of positive discharges.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of hard x-rays emitted from metre-scale positive discharges in air

Kochkin¹,

Nguyen²,

Deursen³

et al. 2012

J. Phys. D: Appl. Phys.

104

138

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We investigate structure and evolution of long positive spark breakdown; and we study at which stage pulses of hard X-rays are emitted. Positive high-voltage pulses of standardized lightning impulse wave form of about 1 MV were applied to about 1 meter of ambient air. The discharge evolution was imaged with a resolution of tens of nanoseconds with an intensified CCD camera. LaBr 3 (Ce + ) scintillation detectors recorded the X-rays emitted during the process. The voltage and the currents on both electrodes were measured synchronously. All measurements indicate that first a large and dense corona of positive streamers emerges from the high voltage electrode. When they approach the grounded electrode, negative counter-streamers emerge there, and the emission of hard X-rays coincides with the connection of the positive streamers with the negative counter-streamers. Leaders are seen to form only at later stages.

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“…Laboratorygenerated negative leaders are similar in structure to their positive counterparts, but they include an additional process referred to as "stepping." As described in Reess et al [1995] and Castellani et al [1998], in the streamer-filled volume ahead of the negative leader, a process referred to as the "pilot" process occurs whereby corona streamers are generated well ahead of the leader tip. Small regions of excess space charge are responsible for generating these coronas and are termed "space stems."…”

Section: Introductionmentioning

confidence: 99%

High‐speed video observations of a natural negative stepped leader and subsequent dart‐stepped leader

Petersen

Beasley

2013

JGR Atmospheres

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[1] We present new high-speed video observations of a natural negative stepped leader and a subsequent negative dart-stepped leader. Observations were made at a distance of 770 m using a high-speed video camera at 10,000 frames per second, a microwave-frequency radio receiver, a broadband electric field antenna, and an avalanche photodiode array. Lightning leader breakdown was observed in detail for both the negative stepped leader and the subsequent dart-stepped leader. During the negative stepped leader breakdown, detailed images were captured of the discharge structures near the leader tips. These structures bear a remarkable resemblance to the corona streamer zone and space leader discharges that have been observed in laboratory-generated negative stepped leaders. During the dart-stepped leader breakdown, no corona streamer zone was observed outside of the decaying return stroke channel, but small luminous structures that are suggestive of space leaders were observed just ahead of the main dart leader tip. Two distinct low-luminosity zones were observed just ahead of the dart leader tip, suggestive of two distinct breakdown regimes. A multipath junction was observed in the main channel to ground following the first return stroke but was not observed following the second return stroke. Finally, microwave-frequency radio emissions for both leader types and their return strokes were recorded, and their time domain behavior is compared and discussed.Citation: Petersen, D. A., and W. H. Beasley (2013), High-speed video observations of a natural negative stepped leader and subsequent dart-stepped leader,

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An experimental study of negative discharge in a 1.3 m point-plane air gap: the function of the space stem in the propagation mechanism

Cited by 54 publications

References 5 publications

Dynamics of streamer‐to‐leader transition at reduced air densities and its implications for propagation of lightning leaders and gigantic jets

Dynamics of streamer‐to‐leader transition at reduced air densities and its implications for propagation of lightning leaders and gigantic jets

Experimental study of hard x-rays emitted from metre-scale positive discharges in air

High‐speed video observations of a natural negative stepped leader and subsequent dart‐stepped leader

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