Modelling effects of electrostatic fields on volcanic ash aggregation.
Costa A., Macedonio G.
During explosive eruptions ash particles are charged by fractoemission and triboelectric processes. Observations show significant electrostatic fields in volcanic plumes and indicate three regions: an upper part with positively charged aerosol, a middle part with negatively charged fine particles, and a lower part with positively charged coarse particles. We model the effects of electrostatic fields on charged ash clusters (due to Coulomb fields, van der Waals forces, etc.) generalizing the Smoluchowski equation in order to conserve also the total charge before and after collisions. We show examples of these effects on the coagulation kernel due to electrostatic forces for typical volcanic plumes.