Charging of droplets by impulse corona

Experiments involving the production of impulse corona of both polarities within a cloud of droplets atomized from a solution of glycerin and water are described. The observed charging of droplets with radii in the range 2.5 to 15 μ is characterized by a maximum surface charge density that is nearly constant down to about 6 μ and increases for radii below that if other electric and geometric parameters are fixed. The largest surface charge densities observed for droplets with radii above 6 μ are approximately 4×10−6 coul m−2 for positive corona and −6×10−6 coul m−2 for negative corona. Our results suggest quite different charging mechanisms for the two corona polarities. With positive corona the droplet charging appears to result from direct interaction between the positive streamers and the droplets. These findings indicate a possible link between the lightning discharge and subsequent rapid cloud droplet growth.