Negative corona discharge at a tip of water cone deformed under dc field

The negative corona discharge phenomena occurring at a tip of water cone have been investigated focusing on the motion and the shape of the water surface using a high-speed video camera. The water cone is periodically formed from a water droplet located on a grounded electrode under dc field due to the electro-hydrodynamic instability. Negative corona discharge with trains of Trichel-like pulses occurred just after the formation of a cone jet. The magnitude and the pulse interval of the Trichel-like pulses gradually increase during the period that the conical surface returns to the initial ellipsoidal shape. The characteristics of the Trichel pulse occurring from the metal electrode simulating the shape of the water surface were also investigated. It is found that the increase in the magnitude and the interval of the trains of Trichel-like pulses with time at the tip of water drop are caused by the corona discharge from the tip of the water surface that deforms from a conical to an ellipsoidal shape.