Corona produced by splashing of water drops on a water surface in a strong electric field

Abstract

Investigations of corona discharges associated with water drops splashing on a water surface in the presence of a strong vertical electric field are reported. When the ambient electric field strength equals or exceeds a critical value, a hydrodynamic instability occurs at the tip of the jet thrown up during the splash. This instability causes the tip suddenly to assume a conical shape from which corona, characteristic of impulse excitation, is produced. The observed critical field strength is inversely related to the falling drop momentum and is independent of the electric field polarity. The minimum critical field for freely falling drops is approximately 1.8×105 V m−1 for 3-mm-radius drops falling at terminal velocity. A quantity of charge in the range 10−7−10−6 C is liberated by each splash depending on the drop momentum and the field strength. This process should be important in determining the response of the ocean to large rapid electric field changes where it is raining.