Influence of grain size and shape on volcanic ash electrical conductivity

Woods, T.; Genareau, Kimberly; Wallace, Kristi L.

doi:10.1016/j.jvolgeores.2020.106788

Cited by 4 publications

(4 citation statements)

References 44 publications

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“…Those results indicate that the mechanisms operating in synthetic solids may not be applicable to natural volcanic materials. More recently, Woods et al (2020) studied the conductivity of a number of ash samples, but did not explore temperature dependence.…”

Section: Discussionmentioning

confidence: 99%

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Microphysical Effects of Water Content and Temperature on the Triboelectrification of Volcanic Ash on Long Time Scales

et al. 2020

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The triboelectrification of ash in low-energy collisions is modulated by humidity 8 and temperature on long timescales 9• The amount of electrostatic charge gained by ash through triboelectric processes is reduced in wet environments over minute-long timescales• The reduction in triboelectric charging efficiency in humid environments suggests that other electrification mechanisms dominate in maturing columns

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Section: Discussionmentioning

confidence: 99%

“…More recently, Woods et al [2020] studied the conductivity of a number of ash samples, but did not explore temperature dependence.…”

Section: Confidential Manuscript Submitted To Journal Of Geophysical Research -Atmospheresmentioning

confidence: 99%

Microphysical Effects of Water Content and Temperature on the Triboelectrification of Volcanic Ash on Long Time Scales

et al. 2020

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“…A large variability of the dataset is also confirmed by the charge-to-mass ratio (~10 −8 to 10 −5 C kg −1 ), a more significant parameter that combines the response to the external electric field and the inertia of the aggregate. In addition, considering that the RH in the atmosphere on 26 November was quite high [i.e., between 60 and 99%; see figure 6K in (33)], we cannot a priori exclude that the presence of conductive water bridges over the surface of ash particles may have acted as a discharging mechanism in specific moments of aggregates formation: This implies that the values for charge should be seen as lower bounds with respect to a dry situation (i.e., RH <31%), for which Woods et al (25) already demonstrated that volcanic ash is a very good insulator. However, Fig.…”

Section: From Single-particle Electrification To the Electrical Multi...mentioning

confidence: 96%

“…At the microscopic scale, charge rearrangement among atoms or the production of free electrons involves several distinct processes ( 20 , 21 ), such as tribocharging due to particle collisions ( 22 ), fractoemission after multiple breakages ( 23 ), and release or absorption of ions contained in the surrounding gas and the induced charge due to background potentials ( 24 ). In addition, Woods et al ( 25 ) have recently shown that volcanic ash is a good insulating material within the range of explored values of relative humidity (RH) (i.e., RH < 31.6%). This suggests that volcanic ash can easily hold the charge and that several electrified patches of different signs can be present on the surface of ash particles.…”

Section: Introductionmentioning

confidence: 99%

First field evidence of the electrical multipolar nature of volcanic aggregates

2022

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The description of the formation of ash aggregates is crucial to our understanding of tephra dispersal and, therefore, to the forecasting of volcanic ash concentration in the atmosphere. Regardless of the importance of electrostatic processes, particle and aggregate charge is of complex determination both in the field and in the laboratory. We have measured the bulk charge carried by single aggregates at Sakurajima volcano (Japan) by inverting the sedimentation trajectory across two high-voltage copper plates filmed using a high-speed camera. Some aggregates were filmed during their breakage caused by the external electric field, which revealed the presence of inner highly charged multipoles with bulk charge up to one order of magnitude larger than the bulk aggregate. This electrical multipolar nature reveals the key role played by multipoles in aggregate formation and the shielding effect of aggregation on particle charge.

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