A lightning initiation mechanism: application to a thunderstorm electrification model

Solomon, Robert C.; Adamo, C.; Baker, M.

doi:10.1016/s1631-0705(02)01415-9

Cited by 8 publications

(3 citation statements)

References 17 publications

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“…However, this value is larger than the RREA threshold field. Indeed, in situ electric field measurements show that the electric field near the lightning initiation point sometimes exceeds the RREA threshold (Marshall et al 2005) It has been suggested that runaway electron avalanches seeded by cosmic-ray extensive air showers (EASs) could result in enough ionization to initiate lightning (Gurevich et al , 2003Solomon et al 2001Solomon et al , 2002Petersen et al 2008). This hypothesis has gained a great deal of attention in recent years, both from the scientific community and from the popular press (Dwyer 2005a;Gurevich and Zybin 2005).…”

Section: Possible Mechanismsmentioning

confidence: 99%

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

2012

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It is now well established that both thunderclouds and lightning routinely emit x-rays and gamma-rays. These emissions appear over wide timescales, ranging from submicrosecond bursts of x-rays associated with lightning leaders, to sub-millisecond bursts of gamma-rays seen in space called terrestrial gamma-ray flashes, to minute long glows from thunderclouds seen on the ground and in or near the cloud by aircraft and balloons. In particular, terrestrial gamma-ray flashes (TGFs), which are thought to be emitted by thunderclouds, are so bright that they sometimes saturate detectors on spacecraft hundreds of kilometers away. These TGFs also generate energetic secondary electrons and positrons that are detected by spacecraft in the inner magnetosphere. It is generally believed that these x-ray and gamma-ray emissions are generated, via bremsstrahlung, by energetic runaway electrons that are accelerated by electric fields in the atmosphere. In this paper, we review this newly emerging field of High-Energy Atmospheric Physics, including the production of runaway electrons, the production and propagation of energetic radiation, and the effects of both on atmospheric electrodynamics.

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Section: Possible Mechanismsmentioning

confidence: 99%

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

2012

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“…Experiments in the laboratory with hydrometeors immersed in otherwise uniform electric fields have shown evidence that dielectric breakdown could be initiated by the locally enhanced fields of these hydrometeors (Dawson and Duff 1970, Craib and Latham 1974, Solomon et al 2002, Sentman and Christian 2005. Theoretically, a conductive sphere immersed in a uniform field will enhance the local field by a factor of three (Stratton 1941).…”

Section: Possible Interpretations Of the Discrepancy In Field Magnitumentioning

confidence: 99%

Problems in lightning physics—the role of polarity asymmetry

Williams¹

2006

Plasma Sources Sci. Technol.

137

148

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Many outstanding problems in lightning physics are linked with a difference in macroscopic behaviour between positive and negative polarity. Such differences are referred to broadly as 'polarity asymmetry'. As specific examples, the positive and negative ends of lightning propagate at different speeds, with different degrees of steadiness, and with different radiated electromagnetic energy. Positive and negative flashes to ground transfer their charge in markedly different ways-negative flashes with multiple discrete strokes (often) and positive flashes with single strokes followed by continuing current. Positive ground flashes cause sprites and negative flashes do not (generally). Positive intracloud flashes send gamma radiation upward to space and negative intracloud flashes do not (generally). Speculative arguments are presented that all of these macroscopic asymmetries are rooted in the microscopic asymmetry in mobility for free electrons and positive ions.(Some figures in this article are in colour only in the electronic version) The thundercloud-the lightning sourceThe two polarities of electricity were identified and named by Benjamin Franklin (Cohen 1990). Franklin also discovered by clever experiment-and it is now well established-that thunderclouds are generally negative in the lower regions but sometimes positive (figure 1). The underlying reason for this well-defined cloud polarity remains elusive even today, though there is abundant evidence that ice microphysics is playing a central role (Krehbiel 1986). The zone of major charge separation-the central dipole region-is invariably characterized by sub-freezing temperatures and contains both supercooled water drops and ice crystals. Curiously, Michael are much appreciated. P Krider provided extensive comments on the manuscript.

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“…Electric breakdown in the first stage of the lightning process, and subsequently the discharge propagation at larger scale, have to be considered. At the present time, two distinct hypotheses may be considered as far as the first stage of the lightning discharge is considered: the runaway electron theory (Gurevich et al, 1992;Gurevich et al, 1999;Solomon et al, 2002), and the microphysical hypothesis in which the hydrometeor surfaces may act as corona emission sites (Crabb and Latham, 1974;Griffiths and Latham, 1974;Blyth et al, 1998;Schroeder et al, 1999;Coquillat et al, 2003). In the following, we focus on the microphysical hypothesis since hail is considered.…”

Section: Discussionmentioning

confidence: 99%

Total lightning activity in thunderstorms over Paris

Boussaton

Soula

Coquillat

2007

Atmospheric Research

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A statistical study of two groups of storms that occurred in the Paris area (France) during summer 2000 has been realized. The first group includes 26 high radar reflectivity (HRR) storms with radar reflectivity values exceeding 60 dBZ while the second one includes 19 moderate radar reflectivity (MRR) storms with a maximum radar reflectivity value between 50 and 55 dBZ. The radar reflectivity was provided by a C-band radar and the total lightning activity (cloud-to-ground (CG) and intra-cloud (IC) flashes) was provided by the French Météorage network and a Safir device. HRR storms seem to be characterized by a longer lifetime, and a more extended convective area. On average, they produce more CG and IC flashes than MRR storms. However, a large variability in the number, the rate, and the type of flashes is observed. The HRR storms producing the highest IC flash rates (above 100 min − 1 ) exhibit the lowest CG flash proportion (1.2 and 4.3%). Most of the HRR storms exhibit a peak lightning activity when the radar reflectivity is strong at low level within the cloud. However, several cases of these storms show a large time lag between the strong lightning production and the presence of high radar reflectivity values at low level. Some possible explanations of these observations, taking into account cloud dynamics, microphysics and lightning initiation, are discussed.

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A lightning initiation mechanism: application to a thunderstorm electrification model

Cited by 8 publications

References 17 publications

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

Problems in lightning physics—the role of polarity asymmetry

Total lightning activity in thunderstorms over Paris

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