Granular electrification on earth and other worlds

Abstract

When mobilized, granular materials, both natural and man-made, become electrified through a variety of processes. The phenomena resulting from such charging can be dramatic, as in the case of volcanic lightning, or quite subtle, like when fine ash particles clump together as they fall through the atmosphere. Despite being recognized in a plethora of natural systems, the microphysical processes underlying the electrostatic charging of granular materials still require clarification. In the present work, we experimentally explore electrostatic processes in both terrestrial systems and those on other worlds in our Solar System and beyond. On Earth, we focus on processes occurring in volcanic plumes, some of the most energetic granular flows on the planet. The motivation for this work is to aid in the development of novel tools that use signals from both lightning and slow-tarrying electric fields to monitor and probe the interior of volcanic plumes remotely. The work involving extraterrestrial systems, namely Saturn's moon Titan and the extra-solar world GJ1214b, explores how charging influences the dynamics of non-silicate granular flows and discharge processes in clouds of exotic materials. As a whole, this work demonstrates the diversity of electrostatic phenomena in granular flows and highlights the need for further research to elucidate their fundamental physical frameworks.