The Influence of Grain Size Distribution on Laboratory‐Generated Volcanic Lightning

Over the last decades, remote observation tools and models have been developed to improve forecasting of ash-rich volcanic plumes. One challenge in these forecasts is knowing properties at vent, including mass eruption rate grain size distribution (GSD). Volcanic lightning a common feature explosive eruptions with high rates fine particles. The GSD expected play major role generating gas thrust region via triboelectrification. Here, we experimentally investigate electrical discharges ash as function varying GSD. We employ two natural materials, phonolitic pumice tholeiitic basalt (TB), one synthetic material (soda-lime glass beads [GB]). For each three coarse fractions known GSDs are mixed, particle mixture subjected rapid decompression. experiments observed using high-speed camera track particle-gas dispersion dynamics during experiments. A Faraday cage used count number measure magnitude discharge events. Although quite different chemical composition, TB GB show similar vent properties. displays significantly ejection significant reduction generation. conclude that coupling an eruption, which turn depends on bulk density, plays defining generation lightning. presence fines, broad GSD, dense particles all promote