Multiphase turbulent flow explains lightning rings in volcanic plumes

Hunga Tonga-Hunga Ha'apai (HTHH), a submarine caldera volcano of the Tonga archipelago, erupted explosively on January 15, 2022. The eruption generated the highest concentration of lightning events ever recorded, producing characteristic ring patterns of electrical discharges concentric to the vent. Here we reproduce the key features of the observations using three-dimensional simulations of buoyant plumes in a stably stratified atmosphere. Our idealized minimal model based on the Boussinesq approximation and heavy particles reveals that the essential mechanism underlying the formation of lightning rings is turbulence-induced particle clustering, which generates structures, favorable conditions for charge concentration by particle collision. We propose that the location, size, and persistence of lightning ring structures can reveal pulsatory activity at the vent that the opaque ash cloud hides from the satellite observation and can be used as a proxy for eruption parameters regulating the generation of hazardous impacts on the environment.