Role of relaxation and contact times in charge separation during collision of precipitation particles with ice targets

Gross, Gerardo Wolfgang

doi:10.1029/jc087ic09p07170

Cited by 18 publications

(14 citation statements)

References 65 publications

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“…The noninductive, ice-ice process is the subject of as much controversy as the water-ice mechanism; however, the controversy does not center around whether the process is effective, but rather on exactly what physical mechanism is responsible for the charge exchange and, to a lesser degree, the magnitude of the charge transferred. Results have been summarized and assessed by Gross [1982].…”

Section: The Basic Charge Separation Mechanisms Included Within the Mmentioning

confidence: 88%

“…The history of laboratory and theoretical work has been a long and colorful one. Stow [1969], Mason [1972], and Latham [1981] provide good summaries, and Moore [1977], lllingworth [1983,1985], and Gross [1982], among others, have provided some critical assessment of various charge separation mechanisms. In general, the charge separation theories fall into two basic categories: (1) those which consider the convective dynamics as the main mechanism which redistributes and organizes already existing charges; and (2) those which consider the charge to be generated by the interaction of hydrometeors (liquid and solid) within the cloud, although the dynamics still act to distribute these charges into the observed structure.…”

Section: Introductionmentioning

confidence: 99%

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A numerical modeling study of a Montana thunderstorm: 2. Model results versus observations involving electrical aspects

Helsdon¹,

Farley²

1987

J. Geophys. Res.

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In this investigation we compare the results of the Storm Electrification Model (SEM) simulation of the July 19 Cooperative Convective Precipitation Experiment (CCOPE) case study cloud against the actual observations with respect to the cloud's electrical characteristics, as deduced from the data of two aircraft. It is found that the SEM reproduces the basic charge and electric field structure of the cloud on a time scale similar to that observed. The comparability of the modeled and observed values of field strength and charge within the cloud is directly related to the proximity of the aircraft to the main active core of the cloud. The character of the electric field external to the cloud appears to be well modeled, at least at the time of observation. A feature which was not observed, but appears in the model, is a charge‐screening layer at the top of the anvil. In addition, the model predicts electric field strengths sufficient to initiate a lightning discharge at approximately the same time in cloud evolution as that when an intracloud discharge was recorded.

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Section: The Basic Charge Separation Mechanisms Included Within the Mmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

A numerical modeling study of a Montana thunderstorm: 2. Model results versus observations involving electrical aspects

Helsdon¹,

Farley²

1987

J. Geophys. Res.

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“…Aufdermaur and Johnson [ 1972], Gaskell and Illingworth [1980], and Gaskell [1981] have shown that large electric charges are generated when an artificial hailstone is exposed to a stream of supercooled water drops or ice crystals in the presence of an external electric field. Gross [1982] has examined the role of collision contact time, the electrical relaxation time, and other physical parameters in these collisions; and Latham [1981] and Gaskell [1981] have concluded that at least the inductive effects are probably not important in terrestrial clouds. Reynolds et al [1957] showed that large electric charges are produced when a hail particle moves through a cloud containing both supercooled water drops and ice crystals.…”

Section: A Liquid Water Cloud Containing 500 Drops CM -3 In Which 2%mentioning

confidence: 99%

“…Marshall et al [1978] have confirmed that charges are produced when ice crystals rebound from a rimed target, and they have also shown that the magnitude of the charge is roughly proportional to the square of the diameter of the ice crystal. More recent work by Caranti and Illingworth [1980] shows that the magnitude of the charging during ice-ice contact is controlled by differences in surface potentials, although the thermoelectric effect is also a possibility [Marshall et al, 1978;Gross, 1982]. Latham [1981] has shown that the ice-ice collisions between small hail and ice crystals are capable of explaining most of the recent measurements in thunderstorm electricity.…”

Section: A Liquid Water Cloud Containing 500 Drops CM -3 In Which 2%mentioning

confidence: 99%

Planetary lightning: Earth, Jupiter, and Venus

Williams¹,

Krider²,

Hunten³

1983

Reviews of Geophysics

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Terrestrial lightning is usually produced by convective clouds that contain supercooled water, ice, and precipitation. Although convection and a variety of mechanisms based on the principle of electrostatic induction can, in principle, electrify clouds, the available evidence suggests that interaction between riming ice particles and supercooled water, followed by a gravitational separation of charged precipitation elements, is the dominant mechanism for cloud electrification on earth. These mechanisms probably operate on Jupiter in the H2O cloud, and optical images of lightning and whistlers have been detected by Voyager 1. Jupiter has no true surface; therefore the Jovian lightning flashes are cloud discharges. Observations indicate that Jovian lightning emits, on average, 1010 J of optical energy per flash, whereas lightning on earth radiates only about 106 J per flash. There is much uncertainty in the average planetary lightning rate on Jupiter, but estimates range from 3 × 10−3 to 40 km−2 yr−1. Venera probes have reported transient LF and VLF radio emissions in the lower atmosphere of Venus, and an experiment aboard the Pioneer Venus Orbiter has registered electromagnetic energy propagating in the whistler mode. Optical searches for lightning on Venus have been inconclusive, but have set an upper limit to the planetary flashing rate of about 30 km−2 yr−1. The Venus observations have led to widespread speculation that there is lightning in the atmosphere, but application of known charging mechanisms to the Venus environment does not suggest that there should be strong electrification. Since the spacecraft observations do not conclusively show that lightning does occur on Venus, we suggest that alternative explanations for the experimental results be explored.

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“…is very attractive in view of its simplicity and the positive feedback that should result in rapid field growth; hoWeVer, because of the finite conductivity of the ice, it is not clear that the charges can flow during the short interaction time available. Gross [1982] pointed out that the relaxation time derived from the bulk conductivity of the ice was much greater than the submicroseCond contact times calculated from HertZian collision theory and deduced that the inductive mechanism should not operate. in an independent analysis of the same problem, Gaskell ['1981• showed that for particles of the size found in the atmosphere the surface con-Copyright 1985 by the American Geophysical Union.…”

Section: Q = (R•/6)(r•/%•)(12r•o%•e Cos •B + Q•)mentioning

confidence: 99%

Ice conductivity restraints on the inductive theory of thunderstorm electrification

Illingworth¹,

Caranti²

1985

J. Geophys. Res.

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According to the inductive theory of thunderstorm electrification, a small ice crystal bouncing off the underside of a larger hydrometeor falling in the presence of an electric field should remove some of the field‐induced polarization charge from the surface of the larger particle; subsequent gravitational separation of the two particles should then result in a rapid growth of the electric field. However, because of the finite surface conductivity of the ice, it is not obvious that the polarization charges can flow along the ice surface in the short interaction time. We report laboratory experiments on the effect of an external electric field on the charge transferred during individual collisions of small (typically, 100‐μm) ice spheres with larger ice targets. When the surface conductivity of the ice was artificially increased by using 10−2 M NaCl, the full theoretical charge transfer was observed, but at 10−5 M NaCl, no field‐dependent charge transfer could be detected. Airborne measurements of cloud and precipitation purity have shown that 10−4 M NaCl is occasionally reached in low‐level stratiform clouds in polluted regions, but even with this degee of contamination the inductive mechanism operates at less than 20% of its potential efficiency at −10°C; at lower temperatures this fraction is reduced still further. We conclude that the inductive mechanism cannot account for the observed electrification of thunderstorms unless other contaminants are having an unexpectedly large effect on the conductivity.

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Role of relaxation and contact times in charge separation during collision of precipitation particles with ice targets

Cited by 18 publications

References 65 publications

A numerical modeling study of a Montana thunderstorm: 2. Model results versus observations involving electrical aspects

A numerical modeling study of a Montana thunderstorm: 2. Model results versus observations involving electrical aspects

Planetary lightning: Earth, Jupiter, and Venus

Ice conductivity restraints on the inductive theory of thunderstorm electrification

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