Electricity in Volcanic Clouds

Anderson, R. V.; Gathman, Stuart G.; Hughes, James H.; Björnsson, Sveinbjörn; Jónasson, Sigurgeir; Blanchard, Duncan C.; Moore, Charles B.; Survilas, H. J.; Vonnegut, B.

doi:10.1126/science.148.3674.1179

Cited by 134 publications

(53 citation statements)

References 14 publications

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“…More importantly, if traps did exist in this range, they would be susceptible to un- loading via visible light (∼ 1.8−3.1 eV). This discrepancy is especially relevant to granular systems continually exposed to visible light from the sun, such as wind-blown dust or volcanic ash, which exhibit strong, same-material tribocharging behavior [3][4][5][6][7][8][31][32][33][34]. We also considered the implications of possible size-dependent electric discharging, which might occur when the electric field at the surface of a particle exceeds the dielectric strength of the surrounding gas.…”

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confidence: 99%

Size-Dependent Same-Material Tribocharging in Insulating Grains

et al. 2014

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Observations of flowing granular matter have suggested that same-material tribocharging depends on particle size, typically rendering large grains positive and small ones negative. Models assuming the transfer of trapped electrons can account for this trend, but have not been validated. Tracking individual grains in an electric field, we show quantitatively that charge is transferred based on size between materially identical grains. However, the surface density of trapped electrons, measured independently by thermoluminescence techniques, is orders of magnitude too small to account for the scale of charge transferred. This reveals that trapped electrons are not a necessary ingredient for same-material tribocharging.

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confidence: 99%

Size-Dependent Same-Material Tribocharging in Insulating Grains

et al. 2014

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“…Luminous discharges are generated in terrestrial volcanic dust clouds (Anderson et al 1965;Thomas et al 2007). Above we see dust particles remain suspended in a gas of number density n = 10 10 to 10 15 cm −3 on scales of several tenths of a km to several km, a plausible venue for large voltages.…”

Section: Coronal Discharge Effectsmentioning

confidence: 99%

Lunar Outgassing, Transient Phenomena, and the Return to the Moon. Ii. Predictions and Tests for Outgassing/Regolith Interactions

Crotts

Hummels

2009

ApJ

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We follow Paper I with predictions of how gas leaking through the lunar surface could influence the regolith, as might be observed via optical transient lunar phenomena (TLPs) and related effects. We touch on several processes, but concentrate on low and high flow rate extremes, which are perhaps the most likely. We model explosive outgassing for the smallest gas overpressure at the regolith base that releases the regolith plug above it. This disturbance's timescale and affected area are consistent with observed TLPs; we also discuss other effects. For slow flow, escape through the regolith is prolonged by low diffusivity. Water, found recently in deep magma samples, is unique among candidate volatiles, capable of freezing between the regolith base and surface, especially near the lunar poles. For major outgassing sites, we consider the possible accumulation of water ice. Over geological time, ice accumulation can evolve downward through the regolith. Depending on gases additional to water, regolith diffusivity might be suppressed chemically, blocking seepage and forcing the ice zone to expand to larger areas, up to km 2 scales, again, particularly at high latitudes. We propose an empirical path forward, wherein current and forthcoming technologies provide controlled, sensitive probes of outgassing. The optical transient/outgassing connection, addressed via Earth-based remote sensing, suggests imaging and/or spectroscopy, but aspects of lunar outgassing might be more covert, as indicated above. TLPs betray some outgassing, but does outgassing necessarily produce TLPs? We also suggest more intrusive techniques from radar to in situ probes. Understanding lunar volatiles seems promising in terms of resource exploitation for human exploration of the Moon and beyond, and offers interesting scientific goals in its own right. Many of these approaches should be practiced in a pristine lunar atmosphere, before significant confusing signals likely to be produced upon humans returning to the Moon.

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“…Since classical antiquity lightnings have been associated with the ashes produced during volcanic activity [1,2]. It has been long speculated that collisional charging may play a significant role in particle's aggregation [3,4] in natural processes such as the formation of planetesimals during the early stages of the birth of a planet [4,5], charging in dust devils [6], lightenings in thunderclouds [7], and electric sparks in dunes [8].…”

Section: Introductionmentioning

confidence: 99%

Early-stage aggregation in three-dimensional charged granular gas

Singh

Mazza

2018

Phys. Rev. E

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Neutral grains made of the same dielectric material can attain considerable charges due to collisions and generate long-range interactions. We perform molecular dynamic simulations in three dimensions for a dilute, freely-cooling granular gas of viscoelastic particles that exchange charges during collisions. As compared to the case of clustering of viscoelastic particles solely due to dissipation, we find that the electrostatic interactions due to collisional charging alter the characteristic size, morphology and growth rate of the clusters. The average cluster size grows with time as a power law, whose exponent is relatively larger in the charged gas than the neutral case. The growth of the average cluster size is found to be independent of the ratio of characteristic Coulomb to thermal energy, or equivalently, of the typical Bjerrum length. However, this ratio alters the crossover time of the growth. Both simulations and mean-field calculations based on the Smoluchowski's equation suggest that a suppression of particle diffusion due to the electrostatic interactions helps in the aggregation process.

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Electricity in Volcanic Clouds

Cited by 134 publications

References 14 publications

Size-Dependent Same-Material Tribocharging in Insulating Grains

Size-Dependent Same-Material Tribocharging in Insulating Grains

Lunar Outgassing, Transient Phenomena, and the Return to the Moon. Ii. Predictions and Tests for Outgassing/Regolith Interactions

Early-stage aggregation in three-dimensional charged granular gas

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