Impulsive Volcanic Plumes Generate Volcanic Lightning and Vent Discharges: A Statistical Analysis of Sakurajima Volcano in 2015

Smith, Cassandra M.; Gaudin, Damien; Eaton, Alexa R. Van; Behnke, S. A.; Reader, Steven; Thomas, Ronald J.; Edens, H. E.; McNutt, Stephen R.; Cimarelli, C.

doi:10.1029/2020gl092323

Cited by 23 publications

(24 citation statements)

References 38 publications

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“…The lightning mapping array (LMA) detects very high frequency (VHF) radiation emitted by electrical discharges during the process of electrical breakdown of air. These instruments were deployed in the Sakurajima region from mid-May to mid-June in 2015 to study volcanic lightning (Behnke et al, 2018;Smith et al, 2018Smith et al, , 2020Smith et al, , 2021. The LMA consisted of nine stations surrounding the east side of Sakurajima.…”

Section: Instrumentationmentioning

confidence: 99%

Observations Show Charge Density of Volcanic Plumes is Higher Than Thunderstorms

et al. 2021

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Electric field change measurements are a key observation to elucidate the physics of lightning discharges. In particular, slow electric field changes, manifesting over timescales of hundreds of microseconds or longer, are produced by the large-scale motions of charge during leader growth, return strokes, and continuing current (Brook et al., 1962;Kasemir, 1960). Coordinated slow electric field change measurements from multiple sites can be used to estimate the locations and magnitudes of the charge centers involved in lightning discharge processes, which, before the advent of radio frequency lightning mapping systems, provided the means to discern the electric structure of storms and how the propagation of lightning is related to and affected by that structure (Jacobson & Krider, 1976;Krehbiel et al., 1979).In the realm of volcanic lightning, much remains to be learned about how charge is organized in the eruption plume, how it evolves over time, and how it affects the production of lightning. Thomas et al. (2010) showed that the electrical activity during an explosive volcanic eruption transitions through three phases: first, numerous vent discharges, on the order of four meters or less, occur within the gas-thrust region of the plume and produce continual radio frequency impulses (Behnke et al., 2021). Next, near-vent lightning occurs at low altitudes in the eruption column, much of which may connect to ground (Aizawa et al., 2016;Cimarelli et al., 2016). These electrical discharges range from tens of meters (Behnke et al., 2018) up to many kilometers in length (Thomas et al., 2010). Lastly, plume lightning occurs in the convective portion of the plume, and is most similar to thunderstorm lightning (

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Section: Instrumentationmentioning

confidence: 99%

Observations Show Charge Density of Volcanic Plumes is Higher Than Thunderstorms

et al. 2021

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“…The onset of an explosive volcanic eruption is often signaled by a swarm of small electrical discharges originating from the vent, in the rising ash column (Behnke et al., 2013, 2014, 2018; Smith et al., 2018, 2020, 2021; Thomas et al., 2007, 2010). These small discharges, referred to as vent discharges, persist for seconds, depending on the duration of the explosion (Behnke et al., 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Observations of vent discharges and volcanic lightning have potential for use in volcano monitoring. For example, CRF impulses occur in impulsive explosive events where the initial velocity of the ejecta is relatively high (Smith et al., 2021). They start occurring at the onset of an explosive eruption (Behnke et al., 2018) and have been observed to persist for seconds to tens of seconds depending on the duration of an explosion (Behnke et al., 2013).…”

Section: Introductionmentioning

confidence: 99%

“…During this eruption, the global lightning data was a boon for the volcano response effort, though the latency between eruption and first lightning detection varied from one minute to one hour. Thus, complementary lightning detection methods, such as a near-range VHF sensing capability, would improve on the latency (Behnke & McNutt, 2014) and provide information related to ash-producing volcanic processes (Smith et al, 2018(Smith et al, , 2020(Smith et al, , 2021.…”

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Radio Frequency Characteristics of Volcanic Lightning and Vent Discharges

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In this study, we analyze the pulse width and spectral content of vent discharges and volcanic lightning flashes. We made measurements of electrical activity with a broadband very high frequency antenna (20–80 MHz) during an explosive eruption of Sakurajima volcano on November 8, 2019. The individual impulses that comprise vent discharges and volcanic lightning were analyzed to determine the fundamental width of the impulses and the rate of fall‐off of their energy spectral density. The results show that vent discharges are more similar to volcanic lightning than they are different. The mean pulse width for both vent discharges and volcanic lightning was 50 ns. Both types of electrical activity had similar spectral content; the average slope of the amplitude spectra was −3.4 for both. Further, examination of the pulse width and spectral slope distributions showed that while the distributions of volcanic lightning and vent discharges are statistically distinct from each other, the distribution of vent discharges is a subset of the distribution of volcanic lightning.

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“…Several observation techniques have been used at active volcanoes to characterize the electrical activity of eruptive plumes, including measurements of electric field variation (R. Anderson et al, ; Kikuchi & Endoh, ; Miura et al, ), direct measurements of fallout‐particles (Gilbert et al, ; Miura et al, ), and volcanic lightning mapping (Behnke et al, ; Thomas et al, ). In attempts to correlate variations in the electrical activity with plume dynamics, some of these studies have employed multiparameter data sets, including infrasound data (J. F. Anderson et al, ; Cimarelli et al, ; Haney et al, ; Smith et al, ), high‐speed video recordings (Cimarelli et al, ), magnetotelluric measurements (Aizawa et al, ; Aizawa et al, ), and seismic data (Smith et al, ).…”

Section: Introductionmentioning

confidence: 99%

Electrification of Experimental Volcanic Jets with Varying Water Content and Temperature

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Cimarelli

Gaudin

et al. 2019

Geophysical Research Letters

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Volcanic lightning-a near ubiquitous feature of explosive volcanic eruptions-possesses great potential for the analysis of volcanic plume dynamics. To date, the lack of quantitative knowledge on the relationships between plume characteristics hinders efficient data analysis and application of the resulting parameterizations. We use a shock-tube apparatus for rapid decompression experiments to produce particleladen jets. We have systematically and independently varied the water content (0-27 wt%) and the temperature (25-320°C) of the particle-gas mixture. The addition of a few weight percent of water is sufficient to reduce the observed electrification by an order of magnitude. With increasing temperature, a larger number of smaller discharges are observed, with the overall amount of electrification staying similar. Changes in jet dynamics are proposed as the cause of the temperature-dependence, while multiple factors (including the higher conductivity of wet ash) can be seen responsible for the decreased electrification in wet experiments.Plain Language Summary Volcanic explosive eruptions are accompanied by lightning strikes generated from the volcanic dust cloud. Here we have experimentally studied the effects of atmospheric water and plume temperature on the frequency and intensity of the lightning strikes. The results will feed a model for the use of volcanic lightning strikes to estimate plume contents and intensity. Key Points:• Natural observations on the influence of temperature and water content on volcanic lightning have been modelled in laboratory experiments. • The magnitude of electrification and discharging in plumes decreases significantly with added water. • At higher temperatures a decrease in magnitude of individual discharges is observed, while the total neutralized charge stays similar.

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Impulsive Volcanic Plumes Generate Volcanic Lightning and Vent Discharges: A Statistical Analysis of Sakurajima Volcano in 2015

Cited by 23 publications

References 38 publications

Observations Show Charge Density of Volcanic Plumes is Higher Than Thunderstorms

Observations Show Charge Density of Volcanic Plumes is Higher Than Thunderstorms

Radio Frequency Characteristics of Volcanic Lightning and Vent Discharges

Electrification of Experimental Volcanic Jets with Varying Water Content and Temperature

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