Correlating the electrification of volcanic plumes with ashfall textures at Sakurajima Volcano, Japan

Smith, Cassandra M.; Eaton, Alexa R. Van; Charbonnier, Sylvain; McNutt, Stephen R.; Behnke, S. A.; Thomas, Ronald J.; Edens, H. E.; Thompson, Glenn

doi:10.1016/j.epsl.2018.03.052

Cited by 24 publications

(20 citation statements)

References 41 publications

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“…These results further to our understanding of volcanic lightning and the electrical characteristics of volcanic plumes. CRF was detected before the eruption column rose above the crater rim and into the line of sight of the LMA sensors; thus, the volcanic ejecta were likely charged prior to exiting the vent (Smith et al, ). However, a net charge from the eruption column was not initially detected until a second or two after the onset of CRF; thus, there was not a significant imbalance in the quantity of positive or negative charge within the eruption column as it was initially ejected.…”

Section: Discussionmentioning

confidence: 99%

Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions

et al. 2018

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Volcanic lightning studies have revealed that there is a relatively long‐lasting source of very high frequency radiation associated with the onset of explosive volcanic eruptions that is distinct from radiation produced by lightning. This very high frequency signal is referred to as “continual radio frequency (CRF)” due to its long‐lasting nature. The discharge mechanism producing this signal was previously hypothesized to be caused by numerous, small (10–100 m) leader‐forming discharges near the vent of the volcano. To test this hypothesis, a multiparametric data set of electrical and volcanic activity occurring during explosive eruptions of Sakurajima Volcano in Japan was collected from May to June 2015. Our observations show that a single CRF impulse has a duration on the order of 160 ns (giving an upper limit on discharge length of 10 m) and is distinct from near‐vent lightning discharges that were on the order of 30 m in length. CRF impulses did not produce discernible electric field changes and occurred in the absence of a net static electric field. Lightning mapping data and infrared video observations of the eruption column showed that CRF impulses originated from the gas thrust region of the column. These observations indicate that CRF impulses are not produced by small, leader‐forming discharges but rather are more similar to a streamer discharge, likely on the order of a few meters in length.

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Section: Discussionmentioning

confidence: 99%

Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions

et al. 2018

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“…Lightning-induced volcanic spherules (LIVS) were first documented in ashfall deposits from the 2009 eruption of Mount Redoubt (Alaska, USA) and the 2010 eruption of Eyjafjallajökull (Iceland; Genareau et al, 2015). LIVS represent an important record of electrical activity within volcanic columns and plumes (Harper et al, 2015;Lane et al, 1995;Miura et al, 2002;Smith et al, 2018;Van Eaton et al, 2016). LIVS were interpreted to result from the high temperatures generated by lightning discharge, which allows melting and morphological alteration of ash particles.…”

Section: Introductionmentioning

confidence: 99%

Lightning Effects on the Grain Size Distribution of Volcanic Ash

Genareau

Wallace

Gharghabi

et al. 2019

Geophysical Research Letters

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Natural volcanic ashfall samples were examined, and high‐current (~100 kA) electrical impulse experiments were conducted to reveal the changes in grain size that can occur during lightning discharge. Experiments on pseudo ash samples manufactured from volcanic deposits of both rhyolitic and basaltic composition show that aggregates of very fine grained ash particles (<32 μm) melt and degas to form vesiculated pumice fragments >100 μm in size. In some cases, bubbles <5 μm in diameter expand and detach from the outer surface of the pumice to form hollow spheres of glass, one type of lightning‐induced volcanic spherule, while other bubbles fragment. Volcanic ashfall from the 2009 Redoubt eruption and the 2016 Pavlof eruption contains both pumiceous grains and individual spherules. Results of this study reveal that volcanic lightning will alter the grain size distribution of ash through melting, vesiculation, and fragmentation of individual particles or ash aggregates.

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“…Thus, if well characterized, these signals may serve to probe the internal, obscured dynamics of eruptive events in manners that have not been achieved previously. For instance, observations during the Augustine (2006) and Redoubt (2009) eruptions suggest that electrostatic processes coevolve with changes in flow behavior (Behnke & Bruning, ; Behnke et al, , ; Smith et al, ; Thomas et al, ). In particular, both Alaskan volcanoes produced two distinct electrical behaviors during their eruptions: (1) initial, quasi‐continual radio frequency (RF) outbursts associated with individual explosions followed by (2) more intermittent, although more spatially extensive, spark discharges in maturing plumes.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, if well characterized, these signals may serve to probe the internal, obscured dynamics of eruptive events in manners that have not been achieved previously. For instance, observations during the Augustine (2006) and Redoubt (2009) eruptions suggest that electrostatic processes coevolve with changes in flow behavior (Behnke & Bruning, 2015;Behnke et al, 2018Behnke et al, , 2013Smith et al, 2018;Thomas et al, 2007). In particular, both Alaskan volcanoes produced two distinct electrical behaviors during their eruptions:…”

Section: Introductionmentioning

confidence: 99%

Inferring Compressible Fluid Dynamics From Vent Discharges During Volcanic Eruptions

Harper

Cimarelli

Dufek

et al. 2018

Geophysical Research Letters

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Observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency (CRF) emissions. The source of this radiation, however, has remained elusive until now. Through experiments and the analysis of field data, we show that CRF originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions. Blasts produce flows that expand supersonically, generating regions of weakened dielectric strength in close proximity to the vent. As erupted material—charged through fragmentation, friction, or other electrification process—transits through such a region, pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge. Discharge is maintained as long as overpressured conditions at the vent remain. Beyond describing the mechanism underlying CRF, we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating CRF sources.

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Correlating the electrification of volcanic plumes with ashfall textures at Sakurajima Volcano, Japan

Cited by 24 publications

References 41 publications

Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions

Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions

Lightning Effects on the Grain Size Distribution of Volcanic Ash

Inferring Compressible Fluid Dynamics From Vent Discharges During Volcanic Eruptions

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