Lightning

Lightning discharges are often observed during explosive volcanic eruptions and are commonly associated with the formation of ash plumes. Lightning discharges are produced within three regions of the plume:

(1) the gas-thrust region immediately above the vent

(2) the convection- driven rising column extending several kilometres above the vent

(3) the neutrally buoyant umbrella region. It is proposed that clustering of particles provides an efficient mechanism for both charge generation and lightning discharge within volcanic plumes.

Clustering can be particularly effective in the presence of prevalently fine ash-laden jets exiting the volcanic conduit. Further charging by magma fragmentation, convection, and buoyancy of particles in the upper regions of the plume, along with the formation of hydrometeors, may provide additional mechanisms of plume electrification.

Lightning is the primary cause of unscheduled interruptions for most overhead power transmission lines and is a major cause of faults on typical overhead distribution lines. Increased lightning discharge activity during volcanic eruptions therefore poses a heightened lightning hazard to power generation sites, substations, and transmission and distribution lines.