Ice needle nucleation and dendrite growth under an electric field

Applying 0.3 to 1.25 kV/cm electric potential gradients to cooled water vapor triggers the copious formation of electrified ice needles, as long as 36 millimeters. This is completely different from the meager ice formation in the same set-up but in the absence of the external field. Needle excess electric charge is evidenced by its attraction towards the electrodes and by its collapse when the field is withdrawn. These observations are explained considering i) the effect of the electric potential on ice surface tension, thus decreasing or eliminating the energy barrier to ice nucleation and ii) the elongated ice habit that allows the accumulation of charge sufficient to create fields higher than those initially applied. The present results show that ice formation under electric potentials that are easily found in natural and anthropic environments enhances charge separation and storage during water vapor condensation and perhaps in other water phase change events.