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  • 1
    Publication Date: 2021-09-20
    Description: Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fluid dynamic and electrostatic conditions. The emissions originate from sparks supported by an electric field built up by the ejected charged volcanic particles. When shock-defined, low-pressure regions confine the sparks, the signatures may be limited to high-frequency content corresponding to the early components of the avalanche-streamer-leader hierarchy. Here, we image sparks and a standing shock together in a transient supersonic jet of micro-diamonds entrained in argon. Fluid dynamic and kinetic simulations of the experiment demonstrate that the observed sparks originate upstream of the standing shock. The sparks are initiated in the rarefaction region, and cut off at the shock, which would limit their radio frequency emissions to a tell-tale high-frequency regime. We show that sparks transmit an impression of the explosive flow, and open the way for novel instrumentation to diagnose currently inaccessible explosive phenomena.
    Electronic ISSN: 2662-4435
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Springer Nature
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  • 2
    Publication Date: 2022-09-09
    Description: Abstract
    Description: This data publication provides data from 42 experiments from 2018 and 2019 in the Fragmentation Lab at the Ludwig-Maximilians University Munich (Germany). The experiments were taken out to analyse the influence of the water content and the initial temperature of the pre-experimental sample on the produced electrification in rapid decompression, shock-tube experiments. All samples used in this study are 90-300 μm loose ash samples from the lower Laacher See unit.To carry out this study, we have built up on previous studies by Cimarelli et al. (2014) and Gaudin & Cimarelli (2019b, dataset to be found in Gaudin & Cimarelli, 2019a). A sample of loose ash gets placed in an autoclave. In our study, we have added water in some experiments. Also, a furnace was often used to heat the sample to up to 320 °C. After both water addition and heating, the autoclave gets pressurized using argon gas. Once a target pressure of 9 MPa is reached, the experiment gets triggered by rupturing metal diaphragms, which rapid decompresses the sample and ejects it into a collector tank. This collector tank is made out of steel and electrically insulated from its surrounding, thus working as a Faraday cage (FC), which is able to detect the net charge within at any point during the experiment. We detect discharges on that net charge up to 10 ms after the ejection of the particles.This dataset contains:- an overview .xlsx file (ExperimentOverview) containing key information for the 42 experiments used for analysis in this study- raw .csv files for all experiments- .pdf files showing the key elements of the analysed experiments, incl. data from Faraday cage and pressure sensorsFor more information please refer to the data description and the associated publication (Stern et al., 2019).
    Keywords: ash ; electric charge ; Faraday cage ; water ; temperature ; shock-tube ; jet ; rapid decompression ; EPOS ; rock and melt physical properties ; multi-scale laboratories ; EARTH SCIENCE SERVICES 〉 ENVIRONMENTAL ADVISORIES 〉 GEOLOGICAL ADVISORIES 〉 VOLCANIC ACTIVITY ; EARTH SCIENCE SERVICES 〉 ENVIRONMENTAL ADVISORIES 〉 WEATHER/CLIMATE ADVISORIES 〉 DUST/ASH ADVISORIES ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 VOLCANIC ACTIVITY 〉 ERUPTION DYNAMICS 〉 VOLCANIC EXPLOSIVITY ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 VOLCANIC ACTIVITY 〉 ERUPTION DYNAMICS 〉 ASH/DUST DISPERSION ; EARTH SCIENCE 〉 HUMAN DIMENSIONS 〉 NATURAL HAZARDS 〉 VOLCANIC ERUPTIONS ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC ELECTRICITY 〉 LIGHTNING ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ATMOSPHERIC PHENOMENA 〉 LIGHTNING ; phonolilte ; ash_and_lapilli
    Type: Dataset
    Format: 2 Files
    Format: application/octet-stream
    Format: application/octet-stream
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