X‐ray bursts produced by laboratory sparks in air

Dwyer, J. R.; Rassoul, H. K.; Saleh, Z.; Uman, M. A.; Jerauld, J.; Plumer, J. A.

doi:10.1029/2005gl024027

Cited by 92 publications

(92 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They were first observed in 1994 from the Compton Gamma‐ray Observatory satellite (Fishman et al, 1994) and later confirmed by other space‐based observations (Briggs et al, 2010; Marisaldi et al, 2010; Smith et al, 2005). X‐rays have also been observed at closer proximity to the source with sensors on the ground and on balloons (Dwyer, 2004; Mallick et al, 2012; Moore et al, 2001) and in high‐voltage laboratory discharge experiments of long sparks (Babich et al, 2015; Dwyer et al, 2005; Kochkin et al, 2014, 2016). The X‐ray and γ ‐ray are produced by high‐energy, runaway electrons through the bremsstrahlung process; however, the acceleration process of these electrons is still under debate.…”

Section: Introductionmentioning

confidence: 99%

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Köhn

Chanrion

Neubert

2018

Geophysical Research Letters

View full text Add to dashboard Cite

Bursts of X‐rays and γ‐rays are observed from lightning and laboratory sparks. They are bremsstrahlung from energetic electrons interacting with neutral air molecules, but it is still unclear how the electrons achieve the required energies. It has been proposed that the enhanced electric field of streamers, found in the corona of leader tips, may account for the acceleration; however, their efficiency is questioned because of the relatively low production rate found in simulations. Here we emphasize that streamers usually are simulated with the assumption of homogeneous gas, which may not be the case on the small temporal and spatial scales of discharges. Since the streamer properties strongly depend on the reduced electric field E/n, where n is the neutral number density, fluctuations may potentially have a significant effect. To explore what might be expected if the assumption of homogeneity is relaxed, we conducted simple numerical experiments based on simulations of streamers in a neutral gas with a radial gradient in the neutral density, assumed to be created, for instance, by a previous spark. We also studied the effects of background electron density from previous discharges. We find that X‐radiation and γ‐radiation are enhanced when the on‐axis air density is reduced by more than ∼25%. Pre‐ionization tends to reduce the streamer field and thereby the production rate of high‐energy electrons; however, the reduction is modest. The simulations suggest that fluctuations in the neutral densities, on the temporal and spacial scales of streamers, may be important for electron acceleration and bremsstrahlung radiation.

show abstract

Section: Introductionmentioning

confidence: 99%

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Köhn

Chanrion

Neubert

2018

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…After the electron flux is computed, the radiated electric field due to the streamer current is calculated by means of equation (6). The spectrum is calculated with the obtained time domain electric field (z, ).…”

Section: Resultsmentioning

confidence: 99%

“…At ground, x-ray emissions are associated at the leader step phase [3][4][5]. These two discoveries promoted the mechanisms of X-ray radiation in laboratory sparks [6][7][8][9]. The investigations show that x-ray primary occur before the breakdown in fast voltage impulses.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic radiation of simulated mid-gap streamers

Montanyà

Fabró

2016

2016 33rd International Conference on Lightning Protection (ICLP)

View full text Add to dashboard Cite

Abstract-Electromagnetic field from simulated double-headed mid-gap streamers is computed. The effect of the applied electric field is studied by considering electric fields higher than the conventional breakdown threshold ('overvoltage'). The obtained results show a 20 dB decay at 3.8 GHz for conventional breakdown electric field, 35 GHz for ambient electric fields five times the conventional breakdown and 170 GHz for fields ten times the conventional breakdown electric field. The limitation in nature of the intense electric fields suggest further experiments using a radio receiver at frequencies of more than 10 GHz in order to investigate the origin of the detected x-rays in laboratory sparks.

show abstract

“…Laboratory tests have shown that long sparks in air are accompanied by a rapid increase in the number of fast electrons with wide energy spectrum (1-300 keV) followed by X-ray bursts and strong flashes of γ photons up to a few MeV possibly related to the runaway breakdown (Gurevich et al, 1999a;Babich et al, 2004;Dwyer et al, 2005;Rahman et al, 2008;Milikh and Roussel-Dupré, 2010). However, these experiments cannot provide us with unambiguous evidence of the leading mechanism of the effect since the applied field was about 1.1 MV m −1 , which is smaller than that of conventional breakdown and greater than that of runaway breakdown.…”

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

confidence: 99%

Underlying mechanisms of transient luminous events: a review

Сурков

Hayakawa

2012

Ann. Geophys.

View full text Add to dashboard Cite

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.

show abstract

X‐ray bursts produced by laboratory sparks in air

Cited by 92 publications

References 15 publications

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Electromagnetic radiation of simulated mid-gap streamers

Underlying mechanisms of transient luminous events: a review

Contact Info

Product

Resources

About