Testing sprite initiation theory using lightning measurements and modeled electromagnetic fields

Hu, Wenyi; Cummer, Steven A.; Lyons, W. A.

doi:10.1029/2006jd007939

Cited by 79 publications

(135 citation statements)

References 41 publications

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“…Because the streamers of prompt sprites are initiated during the rapidly descending stage of the halo, the initial density and field conditions previously used to model an almost stationary halo front are invalid. The measurement-confirmed night-time ionospheric density profile can be used to describe the ambient density condition before the causative lightning 44,45 . The profile is given by specifying an effective height of the lower ionosphere h 0 and the sharpness factor b (see Methods).…”

Section: Resultsmentioning

confidence: 99%

Sprite streamer initiation from natural mesospheric structures

et al. 2015

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Sprites are large, luminous electrical discharges in the upper atmosphere caused by intense cloud-to-ground lightning flashes, manifesting an impulsive coupling mechanism between lower and upper atmospheric regions. Their dynamics are governed by filamentary streamer discharges whose propagation properties have been well studied by past work. However, how they are initiated is still under active debate. It has recently been concluded that ionospheric/ mesospheric inhomogeneities are required for their initiation, but it is an open question as to what the sources of those inhomogeneities are. Here we present numerical simulation results to demonstrate that naturally-existing, small-scale mesospheric structures such as those created by gravity waves via instability and breaking are viable sources. The proposed theory is supported by a recent, unique high-speed observation from aircraft flying at 14-km altitude. The theory naturally explains many aspects of observed sprite streamer initiation and has important implications for future observational work.

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Section: Resultsmentioning

confidence: 99%

Sprite streamer initiation from natural mesospheric structures

et al. 2015

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“…[11] We first estimate the lightning-driven electric fields by applying a method introduced by Hu et al [2007] and Li et al [2008], which combines a deconvolution technique [Cummer and Inan, 1997;Cummer, 2003] and finite difference time domain (FDTD) simulations [Hu et al, 2006]. The deconvolution technique is used to infer the lightning current moment waveform from the remotely measured magnetic fields.…”

Section: Lightning-driven Mesospheric Electric Fieldsmentioning

confidence: 99%

“…All of the sprites analyzed here are produced by positive cloud-to-ground lightning discharges (+CGs), and we use one example to illustrate our approach. Figure 1 shows one example of lightning generated electric fields using the technique described by Hu et al [2007] and Li et al [2008]. Figure 1 (left) shows the measured magnetic fields and extracted current moment waveform.…”

Section: Lightning-driven Mesospheric Electric Fieldsmentioning

confidence: 99%

“…First, we estimate the lightning-driven background electric fields in the mesosphere by combining measurements of lightning radiated magnetic fields and detailed electromagnetic simulations [Hu et al, 2007;Li et al, 2008]. We then measure from high-speed video observations the propagation direction of upward streamers that initiate from the bright core region of sprites.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of electric charge in sprites from optical and radio observations

Cummer

2011

J. Geophys. Res.

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[1] Measurements of very low frequency radio emissions indicate that substantial electric current flows inside some sprites. This charge motion, with presently unknown location and distribution, is related to the detailed internal microphysics of sprite development that is in turn connected to the impact sprites have on the mesosphere. Assuming that sprite streamers propagate along the direction of local electric fields, we combine lightningdriven background electric fields computed from electromagnetic measurements and simulations with streamer timing and propagation direction measured from high-speed images to estimate the total ambient electric field at the locations of upward streamers. From this total field, we are able to establish a lower bound on the electric charge in six observed sprites driven by positive lightning. We find that individual bright sprite cores contain significant negative space charge between −0.01 C and −0.03 C. Accounting for the uncertainty caused by using different vertical charge distribution profiles, these values could be as much as 50% higher. This charge, when spread over the observed sizes of several hundred meters in diameter and approximately 10 km in length, results in a local electric field close to the breakdown field and that the relatively long duration (several milliseconds) optical emissions from this region are driven predominantly by instantaneous local electric fields, in agreement with published simulation results. Given the significant negative charge, we interpret the sprite core region as the partial and perhaps dominant sink of the negative charge created by the downward positive polarity streamers. This further suggests that when downward streamers supply more charge than can be absorbed by the sprite core, slightly delayed upward negative streamers initiate from the sprite core to disperse this charge. This is consistent with observations that show that the subsequent upward streamers are not always present, especially in smaller sprites. Assuming that the sprite core balances all of the positive charge in the downward streamers, we find that the average streamer contains a typical charge of at least 2-4 × 10 −3 dC. Observed sprite current in one bright sprite suggests a positive charge in each distinct downward streamer of only 2.5 times larger than this lower bound, indicating that our estimate of the positive charge in downward sprite streamers and the negative charge in the sprite core is physically reasonable.

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“…It appears that the initiation of the long delayed sprites can be the result of the long-lasting intense CC (about hundreds of ms (Rakov and Uman, 2003) in the positive causative lightning (Reising et al, 1996;Cummer and Füllekrug, 2001;Lyons, 2006;Hu et al, 2007). The important role of higher frequency components (like Mcomponent) in the CC in explaining the long-delay sprites has been suggested (Yashunin et al, 2007;Asano et al, 2009a, b;Kudintseva et al, 2010).…”

Section: V Surkov and M Hayakawa: Underlying Mechanisms Of Transmentioning

confidence: 98%

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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Testing sprite initiation theory using lightning measurements and modeled electromagnetic fields

Cited by 79 publications

References 41 publications

Sprite streamer initiation from natural mesospheric structures

Sprite streamer initiation from natural mesospheric structures

Estimation of electric charge in sprites from optical and radio observations

Underlying mechanisms of transient luminous events: a review

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