Corona Discharges in Atmospheric Air Between a Wire and Two Plates

The corona discharge obtained in atmospheric air between a wire and two plates is presented. For the configuration studied and the voltage applied, the current is steady for the positive corona and exhibits Trichel pulses in the negative corona. The positive corona produces a homogeneous blue halo around the wire, whereas the negative discharge produces evenly spaced spots on the wire surface. We verified the analytic prediction that the ionic wind varies as the square root of the mean current for both the positive and negative polarities. The measured ionic wind produced by the positive corona is higher than for the negative corona. We propose an explanation for the difference of velocity between polarities.