Electric potential gradient changes during explosive activity at Sakurajima volcano, Japan

Lane, S. J.; Gilbert, Jennifer

doi:10.1007/bf00569942

Cited by 58 publications

(53 citation statements)

References 13 publications

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“…This represents a positive above negative charge distribution which is in agreement with the models used by Lane and Gilbert [1992] at Aso volcano, and under certain conditions and for certain samples, net positive particle charges were observed in the Faraday cup experiments. The fact that net positively charged particles were always produced from the lowest silica content pumice (55 wt % SiO2) may suggest a possible geochemical control on net particle polarity.…”

Section: Discussionsupporting

confidence: 88%

“…This implies that although electrostatic forces bind the particles together, fall velocity differences are responsible for bringing the particles together [Lane et al, 1993] The experiments have confirmed the importance of gravitational separation processes for the electrical structure of plumes but suggest that the dipole formation may be a result of complex interactions between ion production and scavenging and particle aggregation. The results indicate that volcanic gases are likely to hold an opposite polarity charge to the net ash charge due to the release of ions during magma fragmentation, as postulated by Lane and Gilbert [1992]. However, variations of particle charge polarity with particle (or aggregate) fall velocity are also likely to be detected as a result of ion scavenging and aggregation processes.…”

Section: Discussionmentioning

confidence: 62%

“…The charge resides on the surfaces of silicate particles and on condensed droplets of volcanic gases, and it probably also exists as ions within the plume [Lane and Gilbert, 1992]. Intraplume lightning flashes and plume-to-ground strikes of both polarity [Hoblitt, 1994] provide strong evidence that different areas within plumes can hold opposite net charges.…”

Section: Introductionmentioning

confidence: 99%

“…It is likely that this dipole structure is formed from the gravitational separation of two components holding opposite polarity net charges. However, it is not known whether these "components" represent either particles of different sizes as postulated by Hatakeyama and Uchikawa [1952] or silicate particles and volcanic gases [Lane and Gilbert, 1992], and the role of particle aggregation in field generation is also unclear.…”

Section: Introductionmentioning

confidence: 99%

“…During and after material fracture, nuclear particles (electrons, positive and negative ions, and neutral atoms) and electromagnetic radiation are ejected from the fresh crack surfaces in a process called fractoemission [Dickinson et al, 1988]. For silicate particles within a plume, Lane and Gilbert [1992] could ascertain no physical reason why particle polarity should be a function of particle size [Hatakeyama and Uchikawa, 1952]. As an alternative they proposed that the opposite polarity net charges are held on volcanic gases and silicate particles rather than on different sizes of particles.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Volcanic plume electrification: Experimental investigation of a fracture‐charging mechanism

James¹,

Lane²,

Gilbert³

2000

J. Geophys. Res.

131

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Abstract. Although ashfall from particulate volcanic plumes is known to be highly electrically charged, little is known about the charging mechanism. We describe experiments designed to investigate the particle charges generated from the fracture of pumice. Small silicate particles were produced in the laboratory during collisions between two samples cut from pumice clasts. The net charge magnitudes detected on these particles are similar to those previously measured on ashfall from volcanic plumes (-10 's to 10 -6 C kg-•). This net charge is also shown to be the result of a small imbalance between the sums of individual particle charges of both polarities, which are up to several orders of magnitude larger than the net charge. The magnitude of both the net and single polarity specific charges were only weakly affected by changes of relative humidity, but single polarity charges increased steadily with increasing sample impact velocities. The dominant charging process during the experiments was that of material fracture. The charging mechanism is thus interpreted to be fractoemission (the release of nuclear particles from fresh crack surfaces) occurring during the production of the silicate particles. This implies that the electrification of volcanic plumes could be the result of brittle fragmentation of magma or pumice clasts within the upper regions of the conduit and in the jet region of the plume.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Volcanic plume electrification: Experimental investigation of a fracture‐charging mechanism

James¹,

Lane²,

Gilbert³

2000

J. Geophys. Res.

131

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The 2010 eruption of Eyjafjallajökull: Lightning and plume charge structure

et al. 2014

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Six Lightning Mapping Array (LMA) stations were deployed in April 2010 around Eyjafjallajökull volcano in southern Iceland. Single-station LMA observations were made during the first explosive period (14-18 April), and three-dimensional LMA observations were made during the second explosive period (5-22 May). The single-station observations revealed that continuous RF electrical activity caused by high rates of small vent discharges occurred during the first explosive period, but not the second, indicating that the strength of vent charging varied between the first and second explosive periods. During the second explosive period, very little lightning was detected between 5 and 10 May, while moderate rates of lightning were detected between 11 and 21 May, signaling that another change occurred on 11 May that affected plume electrification. The data do not make clear if it was changing eruptive activity or changing meteorological activity that resulted in the sudden onset of lightning. The plume charge structure during the second explosive period was inferred from the three-dimensional lightning data, showing that the dominant charge structure varied between a positive monopole and a negative-over-positive dipole. The predominance of a low-altitude region of positive charge and the observation that electrical activity was concentrated near the vent indicate that net positive vent charging was dominating the electrification.

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The effects of dynamics on the triboelectrification of volcanic ash

Harper

Dufek

2016

JGR Atmospheres

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Lightning is often observed during explosive volcanic eruptions, and the charging processes associated with these displays have been attributed to several mechanisms. In this work we delineate a set of experiments designed to quantify silicate-based triboelectric charging in the volcanic context. Using natural samples from three different volcanoes, we show that the rate of triboelectrification in a fluidized bed depends on the energy input into the granular system. Experiments are conducted employing nonintrusive electrostatic sensors, ensuring that all charge exchange arises solely from particle-particle collisions. At higher fluidization energies, particles undergo more frequent and energetic collisions, facilitating the transfer of charge. This finding implies that triboelectric charging could help promote charging in regions of the eruptive system that contain numerous particle-particle collisions such as the conduit and gas thrust regions. Our experiments also suggest that surface charge density is capped, at least in part, by atmospheric conditions, specifically the breakdown characteristics of the gas.

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Electric potential gradient changes during explosive activity at Sakurajima volcano, Japan

Cited by 58 publications

References 13 publications

Volcanic plume electrification: Experimental investigation of a fracture‐charging mechanism

Volcanic plume electrification: Experimental investigation of a fracture‐charging mechanism

The 2010 eruption of Eyjafjallajökull: Lightning and plume charge structure

The effects of dynamics on the triboelectrification of volcanic ash

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