Leader–streamers nature of blue jets

Raǐzer, Yu. P.; Milikh, G. M.; Shneider, Mikhail N.

doi:10.1016/j.jastp.2007.02.007

Cited by 41 publications

(80 citation statements)

References 26 publications

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“…[70] Complementarily, Raizer et al [2006Raizer et al [ , 2007 point out that as the GJ leader propagates upward, the streamer zone ahead of it becomes longer and longer because of the dynamics of streamer growth in a medium with exponentially decreasing air density. Theory of leader discharges predicts the existence of an average constant electric field in the streamer zone equal to the critical electric field value for stable streamer propagation E cr [Bazelyan and Raizer, 2000, pp.…”

Section: Gigantic Jet Acceleration As Evidence Of Its Vertical Structmentioning

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: Gigantic Jet Acceleration As Evidence Of Its Vertical Structmentioning

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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“…Taking into account that τ a ∼ 0.1 µs at the ground level, we obtain τ a ∼ 10 µs at the 18 km altitude, which is typical altitude for BJ nucleation . In this notation, one may expect that the characteristic length of individual streamer, l s ∼ v s τ a (v s is the streamer velocity), cannot be large due to such a small value of τ a (Raizer et al, 2006(Raizer et al, , 2007. For example, a typical length of the streamer filaments propagating inside the sprite is of the order of several meters.…”

Section: Streamersmentioning

confidence: 99%

“…However, such a large value of the thundercloud charges that is required to sustain the BJ seems to be well-nigh impossible (Mishin and Milikh, 2008;Raizer et al, 2010). Raizer et al (2006Raizer et al ( , 2007 have supposed that BJ can be the result of the formation of a bidirectional uncharged leader at the point where the electric field reaches a maximum value inside the thundercloud (see positive peak shown in Fig. 7).…”

Section: Blue Jets and Gigantic Jetsmentioning

confidence: 99%

“…The first group is based on the mechanism of conventional air breakdown, that is, on the thermal ionization of the air by low energy electrons in the presence of electric fields (e.g. see Pasko et al, 1995Pasko et al, , 1996aPasko et al, , b, 1997aPasko et al, , b, 1998aWinckler et al, 1996;Fernsler and Rowland, 1996;Raizer et al, 2007;Krehbiel et al, 2008;Riousset et al, 2010a, b;Raizer et al, 2010). Typical energy of electrons producing the ionization is about 10-20 eV while the mean electron energy is about 2 eV.…”

Section: Introductionmentioning

confidence: 99%

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Underlying mechanisms of transient luminous events: a review

Сурков

Hayakawa

2012

Ann. Geophys.

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Abstract. Transient luminous events (TLEs) occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloudto-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency) and ELF (extremely low frequency) phenomena associated with sprites.

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“…However, likewise customary cloud to ground (CG) lightning, single-headed leaders require unrealistic rates of the thundercloud charge transport. To clear this hurdle, Raizer et al ( , 2007 suggested that the bi-directional uncharged leader (Kasemir 1960) forms in the anvil. As the leader channel transfers the thundercloud potential upward, the overall growth can be maintained by fairly moderate cloud charges and currents.…”

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confidence: 99%

Blue Jets: Upward Lightning

Mishin

Milikh

2008

Space Sci Rev

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Blue jets are beams of blue light propagating from the tops of active thunderclouds up to altitudes of ∼50 km. They resemble tall trees with quasi-vertical trunk and filamentary branches. Their apparent speeds are in the range of 10 s to 100 s km/s. Other events, having essentially lower terminal altitudes (<26 km), are named blue starters. These phenomena represent the first documented class of upward electrical discharges in the stratosphere. Some of upward discharges, termed gigantic jets, propagate into the lower ionosphere at much higher speeds in the final phase. We describe salient features of the upward discharges in the atmosphere, give an assessment of the theories of their development, and discuss the consequences for the electrodynamics and chemistry of the stratosphere. We argue that this upward lightning phenomenon can be understood in terms of the bidirectional leader, emerging from the anvil.

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Leader–streamers nature of blue jets

Cited by 41 publications

References 26 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

Underlying mechanisms of transient luminous events: a review

Blue Jets: Upward Lightning

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