Electrification of Eruptive Plumes Discharged by Shiveluch Volcano in Relation to the Character of the Responsible Explosion

Abstract

It is shown that the rate of explosive eruptions on Shiveluch Volcano has become increasingly high during recent years, which makes the monitoring of the volcano using all available means highly urgent. We seek to introduce another technique into the multidisciplinary monitoring of explosive eruptions by analyzing responses in the vertical component of the atmospheric electric field (E_Z AEF) during the passage of eruptive plumes. We considered two Shiveluch eruptions that were different in vigor that occurred on December 16, 2016 and on June 14, 2017.The signals in the E_Z AEF were selected using multidisciplinary observations, viz., satellite-based observations, seismic, and infrared observations. Signals of negative polarity were recorded in the E_Z AEF dynamics in the near zone (<50 km) for both eruptions at once as ash began to fall. In the first of these cases, the ash–air plume was “dry”; thus, the aero-electrical structure was of the “negatively charged plume” type. The intense explosion that occurred in the second of these cases sent a great amount of ash and volcanic gases into the atmosphere, with 98% being steam; the result was a dipole aero-electrical structure due to eolian differentiation in the near zone. In the far zone (>100 km), the explosion produced a signal of positive polarity coming from an aero-electrical structure of the “positively charged plume” type from the aerosol column.