Problems in lightning physics—the role of polarity asymmetry

Williams, Earle

doi:10.1088/0963-0252/15/2/s12

Cited by 137 publications

(157 citation statements)

References 106 publications

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“…If we assume that a leader could only propagate if it has active negative and positive ends, then the recoil events themselves likely are small bidirectional systems: The original positive leader is their positive end, their negative end crawls back along the previously formed channel system. This was speculated by Williams [2006] and appears confirmed by high-speed camera recordings of Warner et al [2012].…”

Section: Summary Of Observationsmentioning

confidence: 55%

“…Williams [2006] offers an extensive review of the observed characteristics of negative and positive polarity leaders and notes their asymmetry at different scales. Williams and Heckman [2012] proposed that the zero induced charge point remains centered on the conductor, implying that it shifts from the flash origin into the direction of the positive charge region, using a linear potential profile.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetries in bidirectional leader development of lightning flashes

Velde

Montanyà

2013

JGR Atmospheres

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Lightning flashes develop as a bidirectional tree, with a negative and a positive end propagating simultaneously into cloud charges of the opposite polarity. In recent years, this process has been modeled assuming that the bidirectional channel remains a zero‐net‐charge perfect conductor starting at the electric potential of its initial location. So far, both leader ends were treated identically. We summarize characteristics of bidirectional leader development of various lightning flashes registered by the Ebro 3‐D Lightning Mapping Array at the east coast of Spain, supplemented by high‐speed camera records. In order to follow the horizontal development of positive and negative leaders over time, a time‐distance‐altitude graph was designed, using the flash origin or a cloud‐to‐ground stroke as reference. The examples confirm that negative and positive leaders propagate at characteristic horizontal speeds (105 and 2 · 104 m s−1). The positive leader's low apparent speed corresponds to the phase when recoil processes are active. Very fast negative leaders (up to 8 · 105 m s−1) are detected in association with positive cloud‐to‐ground strokes. Negative leaders respawn repeatedly from the origin or as a retrograde negative leader at the positive branch. Positive leaders remain propagating throughout the flash or until reaching ground. We show that the velocity difference shifts the potential of the leader, increasing the gradient with cloud charge at the positive end while reducing it at the negative end. The positive section lowers its potential through retrograde negative leaders, eventually making it possible to emit a new negative leader into the upper positive potential well.

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Section: Summary Of Observationsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Asymmetries in bidirectional leader development of lightning flashes

Velde

Montanyà

2013

JGR Atmospheres

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“…However, negative streamers are clearly present in many natural phenomena of atmospheric electricity like lightning, sprite discharges etc. [1,3,4,5]. Furthermore, modern high voltage supplies easily create negative streamers [2,6,7], and they are very promising for disinfection applications [8] if electrical matching problems can be overcome.…”

Section: Introductionmentioning

confidence: 99%

Positive and negative streamers in ambient air: modelling evolution and velocities

Luque

Ratushnaya

Ebert

2008

J. Phys. D: Appl. Phys.

242

190

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Abstract. We simulate short positive and negative streamers in air at standard temperature and pressure. They evolve in homogeneous electric fields or emerge from needle electrodes with voltages of 10 to 20 kV. The streamer velocity at given streamer length depends only weakly on the initial ionization seed, except in the case of negative streamers in homogeneous fields. We characterize the streamers by length, head radius, head charge and field enhancement. We show that the velocity of positive streamers is mainly determined by their radius and in quantitative agreement with recent experimental results both for radius and velocity. The velocity of negative streamers is dominated by electron drift in the enhanced field; in the low local fields of the present simulations, it is little influenced by photo-ionization. Though negative streamer fronts always move at least with the electron drift velocity in the local field, this drift motion broadens the streamer head, decreases the field enhancement and ultimately leads to slower propagation or even extinction of the negative streamer. Positive and negative streamers in ambient air: modeling evolution and velocities 2

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“…Streamers are used in industrial applications such as lighting [3,4] or gas and water purification [5,6], and they occur in natural processes as well such as lightning [7,8,9] or transient luminous events in the upper atmosphere [10]. Therefore accurate modeling and simulation of streamers is of high interest.…”

Section: Introductionmentioning

confidence: 99%

Deviations from the local field approximation in negative streamer heads

Brok

Ebert

et al. 2007

Journal of Applied Physics

170

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C e n t r u m v o o r W i s k u n d e e n I n f o r m a t i c a Modelling, Analysis and Simulation Modelling, Analysis and SimulationDeviations from the local field approximation in negative streamer heads C. Li, W.J.M. Brok, U. Ebert, J.J.A.M. van der Mullen Deviations from the local field approximation in negative streamer heads ABSTRACT Negative streamer ionization fronts in nitrogen under normal conditions are investigated both in a particle model and in a fluid model in local field approximation. The parameter functions for the fluid model are derived from swarm experiments in the particle model. The front structure on the inner scale is investigated in a 1D setting, allowing reasonable run-time and memory consumption and high numerical accuracy without introducing super-particles. If the reduced electric field immediately before the front is <= 50kV/(cm bar), solutions of fluid and particle model agree very well. If the field increases up to 200kV/(cm bar), the solutions of particle and fluid model deviate, in particular, the ionization level behind the front becomes up to 60% higher in the particle model while the velocity is rather insensitive. Particle and fluid model deviate because electrons with high energies do not yet fully run away from the front, but are somewhat ahead. This leads to increasing ionization rates in the particle model at the very tip of the front. The energy overshoot of electrons in the leading edge of the front actually agrees quantitatively with the energy overshoot in the leading edge of an electron swarm or avalanche in the same electric field. REPORT MAS-E0706 FEBRUARY 2007 Mathematics Subject Classification: 82D10Keywords and Phrases: streamers; ionization front; particle model; local field approximation Note: This work was carried out under project "Multiscale Modelling and Nonlinear Dynamics"-"Electric discharges and plasma technology". The authors acknowledge support by the Dutch national program Bsik, in the ICT project BRICKS, theme MSV1. arXiv:physics/0702129v1 15 Feb 2007Deviations from the local field approximation in negative streamer heads Negative streamer ionization fronts in nitrogen under normal conditions are investigated both in a particle model and in a fluid model in local field approximation. The parameter functions for the fluid model are derived from swarm experiments in the particle model. The front structure on the inner scale is investigated in a 1D setting, allowing reasonable run-time and memory consumption and high numerical accuracy without introducing super-particles. If the reduced electric field immediately before the front is ≤ 50 kV/(cm bar), solutions of fluid and particle model agree very well. If the field increases up to 200 kV/(cm bar), the solutions of particle and fluid model deviate, in particular, the ionization level behind the front becomes up to 60 % higher in the particle model while the velocity is rather insensitive. Particle and fluid model deviate because electrons with high energies do not yet fully run away from the front, ...

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Problems in lightning physics—the role of polarity asymmetry

Cited by 137 publications

References 106 publications

Asymmetries in bidirectional leader development of lightning flashes

Asymmetries in bidirectional leader development of lightning flashes

Positive and negative streamers in ambient air: modelling evolution and velocities

Deviations from the local field approximation in negative streamer heads

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