The effect of air density on atmospheric electric fields required for lightning initiation from a long airborne object

Bazelyan, É. M.; Aleksandrov, N. L.; Raǐzer, Yu. P.; Konchakov, A. M.

doi:10.1016/j.atmosres.2007.04.001

Cited by 24 publications

(15 citation statements)

References 28 publications

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“…It is shown that at any rod height, the critical radius is increased at high altitude. A similar result is found in [31]. It is also shown that the critical radius first increases but ultimately saturates at larger rod heights.…”

Section: Leader Inceptionsupporting

confidence: 78%

Modeling of Lightning Exposure of Sharp and Blunt Rods

Rizk

2010

IEEE Trans. Power Delivery

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Corona characteristics of lightning rods exposed to ambient fields due to cloud charges prior to negative leader descent are analyzed, taking into account rod slenderness and relative air density. A new formula is introduced to account for the effect such corona on upward connecting leader initiation. This quantifies the tendency of a sharp lightning rod towards self-shielding, which can be detrimental to the protection of a nearby object, particularly if this object is less susceptible to corona formation. The effect of corona due to cloud charge fields on the attractive radius of a solitary rod is also investigated. Based on discharge physics, the characteristics of a non-self shielding air terminal are then defined. Since large electrodes are susceptible to deteriorating corona performance due to protrusions and water drops, preference is given to a corona-free rod with the smallest diameter, under cloud charge fields. For tall rods or rods exposed to high ambient fields, however, the required diameter of a hemispherically capped rod may be impractical. The physical approach described in this paper satisfactorily accounts for the lightning performance of competing sharp and blunt rods in a previous field investigation.

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Section: Leader Inceptionsupporting

confidence: 78%

Modeling of Lightning Exposure of Sharp and Blunt Rods

Rizk

2010

IEEE Trans. Power Delivery

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“…The quantitative results of Babich et al [] indicate that the relatively small particles (with ∼0.5–1.5 mm) with a net charge on the order of 100 to 400 pC [ Marshall and Winn , ] are able to initiate a streamer. We note that in Babich et al [], the electric field magnitudes formed on the surface of the particles are mainly controlled by their net charge and exceed those required for initiation of ion corona [ Bazelyan et al , , equation (1)] that would tend to reduce the field by spreading the charge to a larger volume around the particle.…”

Section: Introductionmentioning

confidence: 99%

Initiation of positive streamer corona in low thundercloud fields

Cai

Jánský

Pasko

2017

Geophysical Research Letters

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Formation of filamentary gas discharge forms, commonly referred to as streamers, is one of the conditions required for initiation and subsequent propagation of lightning leaders. It is quantitatively demonstrated that streamers can be initiated under thunderstorm conditions when two precipitation particles cause an enhancement of the electric field by passing in close vicinity of each other. Conditions for avalanche‐to‐streamer transition are documented using a model of two spherical hydrometeor particles placed in uniform ambient field. The results are presented in scaled form using similarity relations for gas discharges and can be applied for a wide range of thunderstorm conditions, including different air pressures, electric fields, and particle dimensions.

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“…In literature, the physical processes leading to the leader onset were theoretically studied in the context of laboratory discharges [e.g., Gallimberti, 1979;Bondiou and Gallimberti, 1994;Aleksandrov et al, 2001a;Vidal et al, 2002;Popov, 2003Popov, , 2009Bazelyan et al, 2007a], where experimental data are available. Similarly, in the context of lightning discharges, numerical models were employed to simulate the inception and propagation of upward lightning leaders from rocket-triggered lightning and tall structures [e.g., Aleksandrov et al, 2001b;Lalande et al, 2002;Becerra and Cooray, 2006;Becerra et al, 2007;Bazelyan et al, 2007bBazelyan et al, , 2008, where ambient conditions can be somewhat inferred.…”

Section: Introductionmentioning

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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The effect of air density on atmospheric electric fields required for lightning initiation from a long airborne object

Cited by 24 publications

References 28 publications

Modeling of Lightning Exposure of Sharp and Blunt Rods

Modeling of Lightning Exposure of Sharp and Blunt Rods

Initiation of positive streamer corona in low thundercloud fields

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

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