Charge injection into the atmosphere by explosive volcanic eruptions through triboelectrification and fragmentation charging

Abstract

Volcanic eruptions are associated with a wide range of electrostatic effects. Increasing evidence suggests that high-altitude discharges (lightning) in maturing plumes are driven by electrification processes that require the formation of ice (analogous to processes underpinning meteorological thunderstorms). However, electrical discharges are also common at or near the volcanic vent. A number of "ice-free" electrification mechanisms have been proposed to account for this activity: fractocharging, triboelectric charging, radioactive charging, and charging through induction. Yet, the degree to which each mechanism contributes to a jet's total electrification and how electrification in the gas-thrust region influences electrostatic processes aloft remains poorly constrained. Here, we use a shock-tube to simulate overpressured volcanic jets capable of producing spark discharges in the absence of ice. These discharges may be representative of the continual radio frequency (CRF) emissions observed at a number of eruptions. Using a suite of electrostatic sensors, we demonstrate the presence of size-dependent bipolar charging (SDBC) in a discharge-bearing flow for the first time. SDBC has been readily associated with triboelectric charging in other contexts and provides direct evidence that contact and frictional electrification play significant roles in electrostatic processes in the vent and near-vent regions of an eruption. Additionally, we find that particles leaving the region where discharges occur remain moderately electrified. This degree of electrification may be sufficient to drive near-vent lightning higher in the column. Thus, near-vent discharges may be underpinned by the same electrification mechanisms driving CRF, albeit involving greater degrees of charge separation.

Ionizing protoplanetary discs in pebble collisions

“…Models range from electron transfer and size dependent charging to exchange of volatiles, i.e. water ions (Duff & Lacks 2008;Lacks & Mohan Sankaran 2011;Waitukaitis et al 2014;Lee et al 2018;Lacks & Shinbrot 2019;Méndez Harper et al 2021;Kaponig et al 2021). Size dependent charging and subsequent size separation might trigger lightning and chondrule formation in a heterogenous cloud with large size differences (Desch & Cuzzi 2000;Muranushi 2010;Johansen & Okuzumi 2018;Spahr et al 2020).…”

“…A natural limit is reached once any further charge would generate an electric field just large enough for breakdown to occur. This does not have to be a large scale thunderstorm but can occur on much smaller size scale (Méndez Harper & Dufek 2016;Matsuyama 2018;Wurm et al 2019;Méndez Harper et al 2021). These discharges can be connected to electromagnetic radiation from optical to radio frequencies (Krauss et al 2003;Méndez Harper et al 2021;Schoenau et al 2021).…”

“…This does not have to be a large scale thunderstorm but can occur on much smaller size scale (Méndez Harper & Dufek 2016;Matsuyama 2018;Wurm et al 2019;Méndez Harper et al 2021). These discharges can be connected to electromagnetic radiation from optical to radio frequencies (Krauss et al 2003;Méndez Harper et al 2021;Schoenau et al 2021). This is well known on Earth, can be applied to Mars (Kok & Renno 2009), and impact ionization in strong electric fields has already been suggested to occur in protoplanetary disks by Okuzumi & Inutsuka (2015) to boost ionization of the gas.…”